Just got the latest issue of Cloth, Paper, Scissors with my article on casting gesso. Loved the metallic gessos by Holbein. They are not inexpensive but so wonderful and worth it. They have a great binder so I was able to cast with them easily. I cast into metal, silicone, latex molds and bubble wrap. This article gives you all the tips and techniques to do this well.
I will also be teaching a class this summer on Mystical, Magical Gesso with a Twist that is the most complete and thorough class on the subject of gesso. This will be with ArtfulGathering.com.