This is something I have wanted to try for a couple of months. So I recently put out a casting for a bald lady and Vonni replied. (Another model sent me a message on Facebook asking why I hadn't asked her to model. The woman had long hair so really wouldn't have come on the radar, but she was most put out that I hadn't asked her).
I asked my mate 
With lots of tubes of latex paint, camera and all manner of pieces of kit I made a slow old trip to the studio and we started the shoot. My idea was to start dripping the paint and shoot steps of the paint building up. The initial shots didn't really look as good a ls I wanted them. The paint also didn't drip as much as I wanted, but if we held the tubes in our hands to warm it up it worked better.
The last shots were of the paint mixed over Vonni's face. She was a gem to work with and I came across some issues and got the solutions for the next one.