I started a griffin months ago using white acrylic paint thinned with GAC 100 for a primer. But I haven’t been able to get the effects I wanted when painting on top of that, and that griffin is still unfinished. Currently I don’t use a primer at all, but go straight to the paints themselves.
For the griffins, I’ve been starting with the lightest one of the colors I plan to use in each area, and dilute the paint down with water. It needs three or four layers to look like anything, but since I layer multiple colors on top of each other anyway it works. For the dragons, though, I love the effects that come from staining the sculpture first. The staining causes random blotching on the scales, but this seems to add depth when transparent colors are added on top. That said, my staining never turns out even. 🙄 I’ve got a lot to learn!