Acetone should take the paint off after a few minutes of being covered in it. Scrub the model over with a toothbrush and nearly all the paint should come off. I woudn't reccommend acetone though, but everyone else seems to like it. Pine-sol is defintely the way to go, i've stripped well over 100 models with it, getting at least 90% of the paint off. Get all the models you want to strip. Put them in some container, tupperware or whatever, and fill it up so all of the models are submerged and leave the for at least a day, 24 hours, doesnt really need to be any longer. Then grab a toothbrush and scrub over the whole model. Also get another container full of water, a cup works. Because I can guarantee that after 10 models your brush is going to be covered in paint and grossness, and you'll be rubbing all that over the models, so just rinse off the brush every once in a while.
Also paint thinner, acetone, does work on plastic. Take a toothbrush, dip it into the acetone and brush over the model, then quickly rinse the model off in water. It takes off some pretty thick paint. Wouldn't reccommend it unless you have some really stubborn paint.
