Hi, all!
I use oven cleaner, too (usually Easy-Off); its active ingredient is lye.
I use an old glass baking dish, place the figures in it, spray a layer of over cleaner over them, and let it work. It usually works relatively quickly, like 5 to 10 minutes to remove almost all paint. Occasionally I come across a figure whose paint is a little more stubborn, and once I did leave a figure in the dish overnight. But in my experience, that hasn't been necessary, and I've found that sometimes, leaving the figure sit too long will allow the softened paint to start to set up again.
I wear cleaning gloves, because lye is very caustic, and use an old toothbrush to remove the goo. Sometimes I will place the dish in a sink and run water over the figure, while brushing.
Also, sometimes it's necessary to use pointed tools, like old dental picks, or sewing needles or pins, to clean out engraved or recessed detail areas.
The cleaner is effective at dissolving old glue, too, so if a figure was glued together, the process can take it back to square one, as a kit for assembly.
Oven cleaner will work to remove paint from plastic models, too.
Needless to say, if you use it, you want to work in a well-ventilated area.
Reagrds,
Brad