Patience, lots of patience. I use acetone free nail polisher remover. And lots of Q-Tips. I prefer Q-tips over the cheap, generic kind. Once the end of a Q-tip gets partially saturated with residue, I change to the other end or use a new one. I usually start at one end and gradually work in one direction. The experience factor definitely helps. Sometimes it helps to do a little bit and then set the casting aside for a day or two before working on it again. This way the paint underneath hardens. On this one I ended up using quite a few Q-Tips.