So the only thing that took the coating off for me was indeed sandpaper but it's absolutely fucked now. I tried tint foil and it did not go well but I assume that's what the heat gun is for. Sadly I havent found a good tutorial for it.

Gave bleach a go to no avail. Also tried alcohol, and a plastic polish. I've tinted a pd-100 mask successfully but the msa outserts seem even more stubborn.