Thanks, Robin.

I did notice that the product description claims that it dries in 30 minutes,
which is a plus as Celluclay apparently takes forever to dry.

I second sculptamold as I picked up the tip from Andy's hobby hq. It doesn't shrink at all.

look up Roman Khramov's videos and how he uses just a thin layer over foam board. Beautiful work. Heavy layers crack over time and any surface can get moldy

I actually use a 50-50 mix of Celluclay and Durhams water colored with kids poster paint. Does not shrink.

Have fun!

I used Celluclay just once. Not only did it shrink and warp, it became infested with weevils (I live in the sunny tropics, aka insect heaven).

I also prefer Durham's Water Putty. Doesn't shrink, and adheres well without any glue. Available in Hardware (DIY) stores, it comes as a dry powder in a can. Build up terrain features with plastic foam, and then mix up Durham's to a consistency like pancake batter and apply it. Follow this with a powdering of dry Durham's straight from the can, which will soak up excess water from the surface, and create an instant, gritty earth texture. You can embed other materials to vary texture or simulate plants, if you like. The putty dries to an earthy, tan color, so no white spots if your paint coverage is uneven. You can also add water-based paint or dry pigments to the mixture to color it all the way through.