SoulSeeker said:
For the love of your health, not to mention the environment, do NOT use brake fluid. It will melt plastic anyway.
Couldn't agree more. Brake fluid is highly corrosive, toxic, bad for you, bad for models, bad for the environment, and all that's before we've tried to clean it up when we're done! It's also very expensive. It will strip paint, but it'l strip everything else it touches!
My personal favourite is a long bath in Methylated Spirit. Methylated Spirit (Meths, as it's more commonly known) is a denatured alcohol and pretty much pure ethanol. It is used more frequently as a fuel source for camping stoves and oil burners, but has great practical uses when it comes to cleaning (I clean the inside of my car windows with it because of a smear free finish), and stripping paint.
It's cheaper than most of the other cleaning products mentioned and beats nail polish remover hands down. After a long soak, an old toothbrush and a needle will get the stubbornest paint from chainmail! I mean what I say about long soak too, I accidently left plastic shields in a bath of meths for 8 months once. They were absolutely fine. The paint, sadly, wasn't. It works a treat on metal too, and is safe on most types of resin. I've not tried it on Failcast...*cough*..ahem...Finecast yet, so I'm not overly sure of its success.
Failing that, simple green is the best product from what I hear, it's just notoriously difficult to get in the UK.
Hope this helps,
u_m