Moisten a sponge with dry cleaning fluid. Blot the stains -- don't rub -- to remove as much of the makeup as possible.
Apply heavy-duty liquid detergent directly to the stains. Rub the pillowcase fabric together to work the detergent into the fibers. Wash the pillowcase in the washing machine using a hot water cycle. Do not machine dry.
Look for makeup stains on the pillowcase after the wash cycle. If stains are still visible and the pillowcase is not white, soak it in a solution of 1/2 cup oxygen bleach dissolved in 1 gallon of hot tap water for at least one hour.
Soak the pillowcase in a solution of 1/4 cup chlorine bleach and 1 gallon of warm water for five minutes if it is white, or if other methods haven't worked. Keep soaking for a few extra minutes if it seems to be working, but don't soak for longer than 15 minutes.