Finger nail polish remover will have other things in it. Use "pure" acetone (As pure as possible, such as found at hardware stores.) It will only affect any organics on the coin. (Oils, grease, etc.) Just use outside with the wind to your back and try to keep from skin contact. Just soak or rinse with it. Don't use anything to scrub or rub with. Any form of rubbing on a coin is the real problem. You can easily turn up with hairline scratches. I have seen a couple examples of modern proofs that were rubbed and the hairlines did show.