Paint removing.
Acrylic paint:
Any alcohol will take it away in a hurry, don't show your models with a whiskey in your hand!
Enamels:
Mr. Muscle oven cleaner or anything with caustic soda in it, be careful as it harms the skin, eyes and pretty much any part of you
Lacquers:
Brake fluid, please test on a scrap piece from the particular model being stripped as it can melt the plastic leaving you with a ill tasting styrene chewing gum
In all cases give it a good scrub with a old tooth brush and some detergent and rinse thoroughly afterwards
Good luck!
Niclas