Etch out the design for your scenery on paper before you begin working. Determine the colors, sizes and placement of each prop in each scene. Lightly draw onto the foam, the designs you plan to cut into them.
Use the scroll saw to cut and shape the larger pieces of foam. The sculpting tool will be used for carving in the smaller details of the designs later. To glue any of the pieces together, use adhesive specifically formulated for polystyrene foam and allow it to dry thoroughly before going to the next step.
Carve the intricate details into the extruded polystyrene foam using the hot wire sculpting tool. The heat of the tools will cauterize the edges, giving them a smooth finish. Take your time and use a steady hand to minimize the possibility of a mistake.
Hard coat the scenery prop with a foam coat or resin that is safe for extruded polystyrene. This will prepare the prop for sanding and painting. Most foam coats dry within 10 minutes, so apply quickly after mixing. If the prop is too large to cover in 10 minutes, mix a small batch and complete the application one section at a time.
Allow the foam coat or resin to dry overnight. Once dry, sand the entire surface of the prop until smooth.
Brush on the first layer of paint and allow it to dry thoroughly. Brush on the second coat. To avoid the appearance of brush strokes, you can stipple on the second coat. To add a gloss or sheen, spray patina on the prop before the second coat of paint dries.