Below is my current understanding of how the armor refinement works. Hopefully, if I'm off on some things, someone will chime in and point it out. I think Barry and Chise have been following all this pretty closely, so I suspect that with their expertise, they have a much better feel for what's happening than I do!
You make plating, thread, or resin for armor refinement from a combination of materials you buy from NPCs (alloy, braid, or flasks, all of which are stackable and should be deedable too) and lootable/stealable items (polish or scour, wash or cure, gloss or varnish). Polish, scour, wash, cure, gloss, and varnish can be found in treasure chests, MIB chests, merchant and pirate vessels. They can also be stolen from containers inside blacksmith, tailor, and carpentry shops in Felucca. They can also be found as loot on the corpses of champion spawn monsters. (I don't know if this means just the bosses or any monsters at a champ spawn and if this is at ANY champ spawn or just the ones in Felucca.) On TC now, you are able to insure these lootable/stealable items, so presumably they will be Siege blessable too.
The wash, cure, polish, scour, gloss, or varnish each come in seven levels (Defense, Shielding, Guarding, Protection, Hardening, Fortification, or Invulnerability) for each type of nonmeddable type of armor to which they could apply and do not stack with each other. (For example, there are two types of nonmeddable armor to which gloss or varnish can be applied after being combined with flasks: Woodland and gargoyle stone. So there are 14 varieties of gloss and 14 varieties of varnish. There are four types of nonmeddable armor to which wash or cure can be applied after being combined with braid: Studded, studded samurai, hide, and bone. Therefore, there are 28 varieties each of wash and cure. There are six types of nonmeddable armor to which polish or scour can be applied after combining it with alloy: Ringmail, chainmail, platemail, samurai platemail, gargoyle platemail, and dragon scale. Accordingly, there are 42 varieties each of polish and scour.)
The level of and the type of armor to which plating, thread or resin can be applied is determined by the level and the type of armor associated with the wash, cure, polish, scour, gloss or varnish from which the plating, thread or resin was created. The level of the plating, thread, or resin is supposed to define the maximum number of resists that have their cap raised and the effect on Max DCI that happens when you apply the plating, thread, or resin to a piece of armor. The Defense Level of plating, thread, or resin is supposed to have the lowest potential to affect all the resists, and the Invulnerability level is supposed to have the greatest potential to affect all the resist caps and Max DCI. You just click on the polish, scour, wash, cure, gloss or varnish (it can be in a container in your backpack) and if you have a sufficient number of alloy, braid, or flasks in the top level of your backpack, you will soon see some plating, thread, or resin in your backpack. The plating, thread or resin will be either a buff/cream color or a kind of coppery color. The lighter-colored plating, thread and resin decrease resist caps and raise Max DCI and the darker-colored ones raise resist caps and decrease Max DCI. Plating, thread, and resin do not stack.
You can make the plating, thread, or resin ANYWHERE if you have the lootable/stealable items and alloy, braid or flasks purchased from an NPC. You buy alloy from blacksmith NPCs. It's not available for purchase from blacksmith guildmistresses or guildmasters, armourers, weaponsmiths, or any other type of NPC you might get smithing BODs from. You buy braid from weaver NPCs but not from tailors, tailor guildmasters or guildmistresses, etc. You buy alloy from carpenter NPCs. You get the idea, I think. Alloy, braid, and flasks cost 50 gp each in both Trammel and Felucca and the available quantity starts at 20. Theoretically, I think this means that if the supply is bought out, it should replenish some time later at double the quantity, up to an eventual maximum available quantity of 1000, with the price always staying at 50 gp.
You use one lootable/stealable component and 20 each of the alloy, braid, or flask purchased from an NPC to craft one plating, thread or resin. Your crafter must have GM-level crafting skill of the appropriate type to make plating, thread, or resin. Braid and alloy each weigh one stone each, so they get heavy quickly when you're trying to use them to make several threads or resins. Alloy is lighter--each weighs 1/10 of a stone, so 20 weighs 2 stones. At the present time on TC, you cannot insure plating, thread or resin and I don't know if that will change before the final publish, so be prepared that these items might be stealable or lootable on Siege when you go to use them at a shop.
The application of plating, thread, or resin to a piece of armor MUST be done at a particular NPC shop and, again, requires GM-level crafting skill of the appropriate type. If you are in the Trammel facet, you apply plating at The Hammer and Anvil shop in Britain, near the conservatory; you apply thread at the Adventurer's Clothing tailor shop in Trinsic; or you apply resin at the Bloody Thumb Woodworks in Yew. If you are in the Felucca facet, you apply plating at the Cutlass Smithing in Buc's Den; you apply thread at the Stitch in Time in Ocllo; or you apply resin at the From Tree to Yew carpenter shop in Jhelom. Inside each of these shops, you will find an "Armor Refiner" NPC. Clicking on the NPC brings up a gump with some basic information about armor refinement. These NPCs seem to have no other purpose at this time.
Each shop has a small area that extends to the front and back of the shop by a few tiles where you can stand to do the refinement (the "armor bonus region"), so you don't have to be inside the shop when you do refining. (When you mark a rune at any of these shops and if you are standing within the specified area, the rune will be marked to say something like, "Armor Bonus Region - Carpenter (Felucca).") If you are standing outside that bonus region and try to apply a refinement by clicking on a plating, thread, or resin, you get a message that tells you that you will have better luck if you go to "XYZ Shop," so just move in closer to the shop (or go to it if you're not already there) and try again. If you're inside the appropriate bonus region, you will get a confirmation gump after first clicking on the plating, thread or resin and then targeting the piece of armor you want to apply it to. Click Yes and you will get a message that you've applied the refinement to the armor. You can be hidden and stay hidden while applying a refinement at a shop. Applying the refinement seems to be a silent process.
Applying polished plating, washed thread, or glazed resin to a piece of nonmeddable armor subtracts 1% from a variable number of resist caps up to all five of them, with the resists that are affected upon application always following a specific order that depends on the type of armor. It also boosts the Max DCI by 2% per number of affected resists. For example, if applying the plating, thread, or resin to a piece of nonmeddable armor only decreases one of its resist caps by 1%, then Max DCI is only boosted by 2%. However, if the application of the plating, thread, or resin decreased all five resist caps (each by 1%), then the boost to Max DCI will be 10%.
Applying scoured plating, cured thread, or varnished resin to a piece of nonmeddable armor adds 1% to a variable number of resist caps up to all five of them, again with the resists that are affected upon application following a specific order that depends on the type of armor. Using scoured plating, cured thread, or varnished resin also lowers the Max DCI by 2% for each affected resist cap.
So far it appears that you can apply armor refinement to armor pieces that were previously crafted or enhanced out of special materials and/or that have been imbued or to looted armor pieces, but only if they aren't already meddable or have the mage armor property on them. You can imbue or enhance nonmeddable armor that has already been refined (e.g., bump its resists) without losing the refinement modifications. However, you cannot imbue the mage armor property onto a piece of nonmeddable armor that has already been refined--the Mage Armor property simply doesn't come up as an option on the Imbuing gump. It appears that at this point there is a small chance you can enhance woodland armor with heartwood to add the Mage Armor property (I got it to work this afternoon), but I don't know if that will make it through to production shards and you will probably break a lot of pieces trying to make it happen if it does.
Gheed posted in the UHall thread his analysis of the order in which the resist caps are affected by armor type in this post:
http://stratics.com/community/threads/uo-com-updated-publish-81-on-tc1.295073/page-4#post-2242833 . However, here's a copy of Gheed's table just to make it easier for you:
What that chart means is that if you apply one of the resins to a piece of woodland armor, for example, and only one resist cap is affected, it will always be Cold. If the roll of the dice for the refinement action says "affect 3 resist caps," it will always be the Cold, Poison, and Physical resist caps that are affected. There will always be at least one resist cap affected (-1% or +1% depending on what you used) and Max DCI will always be affected by at least 2% (bumped or decreased, depending on what you used).
Now what blew me away, after seeing all the possible types of polish, scour, wash, cure, gloss, and varnish (7 for each one of those TIMES all the nonmeddable types of armor to which each could apply!) and then playing around with actually applying some of them to nonmeddable armor at the NPC shops in town, was that the actual result of the application is RANDOM! What I mean is that there appears to be a possibility that you could end up with all five resist caps being affected by using Polished Plating of Defense, or you could have that end result using Polished Plating of Invulnerability. Apparently, though, the chances of all 5 resist caps being affected with the Polished Plating of Defense are lower than if you used the Polished Plating of Invulnerability. Also important to note is that it is apparently possible to apply refinements an unlimited number of times to each piece of nonmeddable armor, i.e., until you get the result you want. Each application overwrites the refinements made with the previous application.
Barry has posted here some examples of how the "Max DCI" from the refinements works with respect to DCI over-capping and HLD:
http://stratics.com/community/threads/uo-com-updated-publish-81-on-tc1.295073/page-4#post-2242902 . I have to admit, this is where I start getting glassy-eyed, because I just don't usually worry about DCI and HLD because I don't usually fight much of anything toe-to-toe (I mostly play tamers and crafters these days). Hopefully he can jump in with some more information here. I made myself go start looking at the armor refinement stuff on TC because I have a strong feeling that this is just the first chunk of it, as it only affects nonmeddable armor (i.e., metal, dragon scale, studded, hide, bone, woodland, and stone armor). I keep thinking that the dev team is going to roll out another set of refinement components that will be combined with braid and maybe other materials to produce thread and other items to refine meddable armor resist caps and some property that is valuable to spellcasters.
So, if you made it all the way down to here with reading and somehow what I wrote makes some kind of sense and doesn't just read like gibberish, I guess take heart that it doesn't look like at this point it's going to be necessary to stockpile 336 different kinds of polish, scour, wash, cure, gloss or varnish. If you want to refine something, you might just use what you have on hand and hope it affects the exact number of resist caps you want to have affected and creates a Max DCI modifier that you want. And if it doesn't work, you pick out a different one, cross your fingers, apply it and hope that it worked. If you want a stronger effect, you go with something that is at one of the "higher" levels e.g., Invulnerability, Fortification, or Hardening) and hope the RNG lets them affect as many resist caps as possible. If you want less of an effect, you use a plating, thread, or resin of a lower level (Defense, Shielding, or Guarding) and pray the RNG lets the refinement affect only one or a few resist caps.
Let me know if you spot anything wrong in this and I'll be happy to fix it.