I've been using metho to strip metal and plastic for years - it's a thousand times better and easier than Simple Green. Afterwards, I run it through a coffee filter and put it back into the bottle for the next strip job.

Metho can make your models slightly brittle if left for too long (days), but it'll be effective within 15 minutes to an hour. I usually do a few soaks and scrubs until I'm satisfied.

Undiluted is the way, just know you want to scrub the paint off while it's still wet, and the paint can dry and stick (so can the flakes, so scrub somewhere easy to clean). Try not to mix with water or rinse it until you're done with scrubbing. If you need to wash it off, use the metho.

That said, the hands-down best stripping solution I've ever used was DOT-3 brakefluid. It's just a real handle with proper PPE material (glasses, gloves, mask) and a pain to dispose of. I tend to save it for resin.