Cosplay Pros Foam Clay is the best way to add small details to your cosplay builds. The clay comes in 150 gram as well as 300 gram tubs. Simply mold the foam clay into your desired shape and allow to air dry for 24 to 48 hours. It will magically cure into a dense foam, allowing you to cut it, sand it, and of course paint it too! This is a must-have product for your cosplay arsenal.