Fishing rods!
Equip a fishing rod and fight a golem in tram, unguilded.
You have to stand on the same tile as the golem for it to work.
With the fishing rod you will gain in wrestling while swinging at 1.25 instead of the standard capped wrestling swing speed.
You can also fight npc warriors in fel but the fishing rods break very freequently, where as, against the golem you will be able to use the same rod all the way to 120 and best of all the golem doesn't even take damage.
(It was around a year ago I used this method, so there is a chance there may have been a change to the way gains work with golems in tram while unguilded - I highly doubt it but you never know. If you aren't gaining after a while of banging on the golem, I would recommend going grabbing an NPC warrior from Jhelom pits, gate to a fel harbour and have the NPC attack you. Make sure you have a decent amount of gold to keep restocked on Fishing Rods because you will go through them fast.)