One thing I've noticed is that a number of the spray-cans labeled "acrylic" or "lacquer" are methanol resistant but wipe almost straight off if you expose them to nitromethane.

Modern synthetic oils are also a problem. In fact, some paints will stand up reasonably well to low-nitro fuels but just disolve away if hot synthetic oil from the muffler sprays against them.

I guess one option is to use no nitromethane and stick to castor oil. Hey, FAI fuel could make a come-back :-)