Place a stack of paper towels on a level surface. Turn the washable fabric inside out and lay the stain on the paper towels. Keep the nail polish facing down.
Dampen a cotton ball with acetone. Dab the back of the dried nail polish stain with the cotton ball. Replace the soiled cotton ball with a clean one when it becomes dirty.
Blot the dried polish for several seconds. Hold the fabric under cold running water to rinse off the acetone.
Repeat Steps 1, 2 and 3 until you remove the dried nail polish. Rub a prewash stain treatment into the fabric's fibers and let it sit for 10 minutes.
Launder the washable fabric as you normally would.