+1 on the acetone. Most "nail polish remover" is made from acetone with a little lanolin or something similar added so it's virtually the same thing as acetone; just way more expensive. Some rattle can paint will not respond to acetone so try a small spot first. If that doesn't work, a more agressive approach might be some lye based paint stripper, but be very careful and work with small areas. You should be able to time it so that the stripper will only have time to attack the fresh paint and get it off before it attacks the original paint. Also, be aware that this stuff will remove skin as well as paint. Wear all recommended protective gear and carefully follow directions if using this method.