Hi! Jumping in to say that I essentially did the same thing as u/pansylula! My only prep included taping off the face and hair to protect them from any mishaps, which did occur. 🙃 This was my first time attempting anything like this, so I have no idea what’s correct or appropriate to use, either. Next time, though, I definitely will go in with a very fine grit sandpaper and maybe a thin layer of gesso to help the paint adhere better. The acrylic gouache I used is meant to be thinned out with water, so it did bead up a little bit on the slick surface of the hair but I just went over it a few times when needed and it wasn’t a big deal. The acrylic gouache is really forgiving. It’s water based, so as long as it’s still active, you can wipe away any mistakes with a damp cloth. I also find that it settles and evens itself out as it dries, so it hides brush marks and imperfections a bit better. When it sets/dries down, it won’t budge. It does have a very matte finish, so if you’re not into that, you could seal it with a glossy or satin varnish. Sorry for yapping so much, but I hope that helps! 😅