I've only tried to remove paint from miniatures once in the past. That was about seven years ago and it was a bunch of 1/72 HAT plastic Napoleonic miniatures. I used an oven cleaner to spray all over the figures and then left them to sit for a day or two. It worked reasonably well as a paint stripper but I had to be careful with the noxious fumes and also wear protective gloves and eye wear.
I've been reading on the Internet of the merits of brake fluid as a paint stripper that's safe to use with plastics. I decided to try it on a bunch of Moria Goblins I'd picked up really cheaply on eBay. These figures had paint jobs that left a lot to be desired and as I intended to repaint them, the original paintwork needed to be stripped.
I dumped 87 of the little blighters into a container and covered them with brake fluid. I then left them to soak overnight. 24 hours later I grabbed an old toothbrush and was pleasantly surprised to find the paint just sloughing off. The figures weren't harmed at all and the brake fluid combined with some scrubbing removed probably 95% of the previous paint job.
Some had broken weapons when I got them so they'll be used for conversion purposes.