Jeff Sessions forehead grease works best. If that doesn't work, then I suggest Methyl ethyl ketones, which I use to clean my dinghy at the end of the season of hard use.
Interestingly I used to clean Sharpy indelible ink off of Xray film{mis- labeled affected side} by drawing over line with fresh Sharpy mark and immediately wiping with an alcohol wipe. This has also worked on other plastics. If all else fails try toilet cleaner gel made for under the rim, it has muriatic acid. Wear gloves rinse with water no metal containers or scrubies.