After woodworking it was time time to add ballast to the track and cover the plywood pacific with something that does a better job in imitating nature. First I painted the surface in colors to match the later usage (brown for dirt and grass, gray for gravel and roads). The next layer is sprinkled over most areas with colored, flexible gap filling putty (like Lugato Universal-Fuge-Flexibel). You can get it in different sized bags and multiple colors which can be mixed to create an interesting and varied surface cover.