You need acetone nail polish remover, cotton swabs or balls pulled apart in to tiny bits, and a strong thumbnail. Use a wet bit of cotton and your nail to scrape the paint off. Keep switching out to clean bits. If you have smudges rinse with water, dry, and let rest before wiping again.
Now I also discovered if you put a Monster head in a bowl or mug of water in the microwave and cook it for a minute or so you can soften the paint and scrape it off with your nail. I used to use hot water to soften rooting glue in their heads. Microwave doll heads at your own risk.