Infectious Strike is hands down the best way to work poisoning.
You can gain from 50-GM by blitzing through the 2nd and 3rd levels of Despise and Infectious Striking everything that moves (minus the Ogre Lords and the Acid Eles, of course).
It shouldn't take you very long at all to get to 80 if you have a fencer (even a swordsman--but you're limited to cleavers only I think). Get a bag full of crappy kryss and daggers and pre-poison them prior to entering the dungeon. Change them out as they run out of charges. Hit everthing--don't stop to loot and don't stop to finish anything off (you'll get them all dead after a few passes anyway). When all your weapons have run out of poisoning charges---repoison them and do it all over again. The gains are so fast it's not even fair.