I'm working on a 1/2" masonite panel with a ground of Liquitex modeling paste which is composed of a polymer and marble dust. I apply it with a trowel and then sand it very smooth. I'm working in thin layers of oil over this surface--it's kind of absorbent which is working well for me. The surface dries much faster than on a gesso ground so I can work the layers in the same session. I'm thinking about applying a layer of clear encaustic medium over the finished painting. More of these on my website on the "On My Easel" page.