I usually use concentrated simple green, diluted very little if at all. The last time I used it was to strip a Necron destroyer, and after three hours in the mix (prolly a 3:1 simple:water ratio) it came out pretty paint free. I didn\'t even have to scrub it, it all just sort of floated off.
It hasn\'t deformed my plastics yet, but I never leave it in for too long either. Maybe five hours, tops. It\'s all you need really.
The only thing I find that it wont get off is a certain type of krylon that bonds to plastic. It takes off most of it, but the mini still looks pretty black. And also, I did leave a metal guy in over night once, to find that some areas got sort of discolored. It didn\'t effect its ability to hold new paint though.