I'm hardly a master painter but I'll throw in what I do know. Are you looking to remove a paint blotch but preserve the coat of paint underneath? Unfortunately, I think that'll be pretty tough to accomplish.
I have never found rubbing alcohol effective for removing paint. Acetone will take the paint off, but it is pretty strong and you're going to risk taking off more than you want. Maybe if you use a little bit on the end of a q-tip, but even then it'll be hard to avoid removing the coat underneath. You can try lightly sanding the blotches off, but you're risking damaging the undercoat as well.
You can use acrylics or enamel to repaint, just make sure to prime the piece first. Tamiya acrylic paints are an excellent brand. I find enamel to be a pain in the butt to use because of the drying issues.
There is a lot of great info in the "Painter Section" for beginners. You should definitely surf around there. Good luck!