I made a batch of plaster ("Plaster of Paris") and dipped strips of newspaper in the plaster. Draping them over the first layer of newspaper was all it took to get a nice shell. As the plaster started to harden up, without letting it go to waste, I dipped my finger in the mixture and spread it over the uncovered areas. Although newspaper is still visible, painting and scenicking the whole thing in the future will hide all that.

The strong vertical surfaces I want to cover with castings. Because I placed the "ridge" too close to the track I had to make some thin castings (see my article on how I made them). I then broke them up and glued them in place with a Liquid Nails adhesive. This next photo shows some of the pieces already glued in place. Many more need to be made and installed.