My experience:
WARNING!
Most compounds that can take off paint are toxic in some way or another. If you are using these chems do take care with their use and disposal.
Brake fluid: One of my favorites cause It won’t eat the plastic minis. if you soak the mini in the brake fluid for a few days you can toothbrush away the paint. It does have an odor and can be difficult to clean off completely
Pine sol: soak a day or so and it removes paint from metal minis and softens plastic minis and bases. Not too toxic and females may equate the scent to cleanliness.
Acetone [Nail polish remover’s main ingredient]: Great for metal minis, eats superglue, eats plastics, eats skin, stinks like hell You can use the nail polish remover to soak your minis but pure acetone is much faster/ stronger. You can get pure acetone at most Beauty Supply Stores along with chemical suppliers. [it might eat plastic pipes, dilute before pouring down the drain unless you want to risk costly home repairs]
BTW
1. If the mini has some very small crevasses you may need a toothpick to get in the small openings
2. Avoid mixing these chemicals together. I got no Idea what may happen if you do mix them.
3. Put minis into a glass jar and let them soak OUTSIDE your home. Few things eat glass and fumes are best kept outside your dwelling. { I had to use a Gallon pickle jar to clean the tire glue[ a THICK black cyanocrylate based glue in the superglue/crazyglue/zap-a-gap family of glue] off of the WotC Black dragon I bought from a friend who had NO modeling experience and tried to put it together.}
4. Wash minis thoroughly after cleaning them of paint.
5. If the Mini has a lot of glue / epoxy putty work taking the paint of will likely dissolve the putty and glue off.
I have heard about these BUT I have not verified if they work:
Rubbing Alcohol: works on metal, safe on plastic.
Simple Green. Strips acrylic paint won’t eat plastic.
Oven cleaner: some say it won’t eat plastic others say it will. Strong odor.