Model Railroad magazine has a bunch of aticles on making trees. Of course most of the articles are for HO scale, but all you have to do is scale up. There was one really good article about using sticks from the yard or from a flower shop. Using spray glue or even cheap hair spray. Spray the twig and then put it in a plastic bag with the color of ground foam you want and viola, instant trees. Just an idea. If I hadn't put all my railroading mags up, I would try and find the article. Well maybe later. hope this helps or at least gives an idea.

Jim