Cotton gloves.
Yes there IS something that you can paint on your dolls to "bombproof" the faceup.
Minwax Polycrylic Floor Sealer.
It also comes in a spray, but I have not tried the spray yet.
http://www.minwax.com/wood-products/interior-clear-protective-finishes/minwax-polycrylic-protective-finish
The problem is it doesn't come in a true matte finish. It comes in an almost-but-not-quite matte. So your doll's face will always be shiny. I have not yet tried it with a coating of MSC over the top. I *have* used it on my Dollzone Water Dragon's body painting (because a dragon should have shiny scales anyway) and it wears like...a floor. Seriously bombproof. It is completely safe for resin.