Try a mix of Dawn and hydrogen peroxide in an area. Put it into a bowl or old cup. Mix it with a paint brush and brush it on in a spot. Let it sit for a couple minutes. then use a paper towel and see if it comes off. If that doesn't work try a micro fiber cloth or one of those MR. Clean eraser mates sponges or even a little very fine steel wool. I know acetone would work but it might take the paint off.