Post bump as I have been having the same issue…
First H2 I got I just painted right over it, didn’t remove the hair, didn’t even use liquid latex, didn’t seal it at all. 10 years later and it still looks great, sure it will crack if I touch it but it’s for display. I had no idea what I was doing but wanted to make it look better. The mask actually started rotting before the paint was an issue.
Seems the newer (last 5 years?) TOTS maks have a different sealer that is glossy and doesn’t let new paint stick, so ideally you just strip that with lacquer thinner and paint over it.
The problem, for me, comes when I tried to remove the front hairline for better painting- you pull it and it rips off the latex paint layer with it and once it starts peeling, you pretty much have to remove it all (or 99% of it) or you see the lines/seams under the new paint. I got lazy and gave up on one, and you can defintely see a line but it’s not a big deal if you’re doing a really dirty mask OR the lines end up on the ear or an inconspicous area.
The H4 Poster mask I did peeled off in big chunks, it was really easy. The last few bits I used the felt Dremel bit on the lowest setting and it got a lot of the rest off. There were still some stubborn areas that I did my best to smooth/feather the edges with the dremel on a slightly higher setting. You can feel and smell when you’re on the latex as opposed to the paint. I wasn’t able to get some off the ears or in the mouth at all, so I just left it. There was one spot of paint that felt harder in the eye socket, and it actually started pulling the latex off with it- I noticed just in time and was able to snip it off and smooth the eyecut with the dremel, but it could have ruined the mask! So be careful.
So in summary, try not to peel ANY of the paint if possible. Just clean the sealer.
Once it starts peeling, hope you get big chunks. Otherwise, it’s the felt tip dremel on low until you can’t take it anymore, and feather what is left making sure it’s not in the middle of the cheek or head. Lacquer thinner didn’t remove paint for me, just made it less glossy (removing the sealer I think). And I didn’t want to damage the mask, it didn’t seem like a feasible method.
I have a bunch of hair to rehair some masks with, but I’m really hesitant to start pulling hair for this reason- I wish there were something to really soften/remove the glue before you pull it. Or just snip the hair to the roots and leave the glue? I don’t know, but once that paint starts peeling it becomes a nightmare that you can’t give up on.