I use a product called taskboard. Comes in different thicknesses and can easily be cut or trimmed with a hobby knife or even a scissor so curves and other shapes are not a problem. It has a very light textured finish which adds to the the realism. Easy to paint too. Another material you could use in Sintra, a poly product that is harder to cut but is stiff and works well. And of course there's MDF, available at big box hardware stores but I believe you'll need a power saw to cut and make curves. Hope this helps.
Jerrman
