As Ron has said, soaking the model a second time and using an old toothbrush should work very well for you. On occasion, a particularly stubborn area may require an application of very fine sandpaper (800 or finer). However, what ever you do, don't use thinner to remove the paint as it will melt the plastic. (Most of the liquids used to thin acrylics won't effect the surface, but by the same token, won't effect the paint either). If you want to see for yourself, take a small piece of sprue from the kit, put it into a glass jar, pour in enough thinner to cover the sprue, put the top on the jar and let it set for a couple of hours and see what happens.