In this video I make a tunnel form my layout
I used wire mesh to make the form of the tunnel
Next I covered the form with Plaster Cloth which is available at store such as Hobby Lobby and Micheals. Also available online thru Amazon.
Finally I put a layer of American Art Clay Sculptamold which is available thru Amazon or your local hobby shop. Here’s a link to it on Amazon
American Art Clay Sculptamold 3 lb Bag https://a.co/d/5k1NjVb