Backyard lost foam aluminium casting

Hi guys ,
some youtube video to share with my last home lost foam casting ( very simple models).
i would be interested to try it in sand with liquid coating but would need a simple recipe for the coating . if someone can help me it would be very nice.

part 1: foam models making https://www.youtube.com/watch?v=6Ng900w9euk
part 2: mold making : https://www.youtube.com/watch?v=MfZdFEzOKDA
part 3: aluminium casting: https://www.youtube.com/watch?v=AXEEMhkgFvE
part 4: mold release: https://www.youtube.com/watch?v=JUj1kANFbJ8

I've heard of people using a thin layer of wallboard joint compound to coat their foam models prior to casting, but I've never tried it myself. Make sure to let it dry out thoroughly before pouring the hot metal on the foam.