From this question:
It sounds like goof off is a product you might try. Good luck.
It depends on the type of paint and the type of clothing. If it has dried, and it is acrylic, you might as well just throw it away. The best thing that I could recommend is to go to an art supply store and get something called "brush cleaner" in a small little, round, plastic container. It will take a while but it will eventually loosen up ANY kind of paint- even acrylic.How do I get paint to wash out of clothing?