There are several chemicals that will work for removing enamels from plastic. Check your lhs. Easy Off Oven Cleaner will work, but I don't use it because it's somewhat caustic. I myself prefer to use automotive brake fluid. You need to find a pan that is large enough and deep enough to hold your model. Pour enough brake fluid in to just cover the model and let it set for a day or two. The biggest percentage of the paint will come off in the pan as you remove the model. Have a toothbrush, some fine sandpaper (600 grit works nicely) and some toothpicks on hand to remove stubborn spots.
When you finish wash the model in warm water and mild dishwashing liquid (at least twice) and then rinse. When dry, its ready to repaint. The fluid in the pan can be filtered and put back into the can. (a pair of my wifes old panty hose works great for filtering). You can get quite a few models stripped out of a quart bottle of the fluid. Just don't use it in your vehicle after you start using the fluid for stripping.
No matter what you try, you need to try it on an old paint hulk (you know, the model you really screwed up and now use for adjusting your paint mixture) Good Luck