Here are some shots of my efforts at a Halloween scene. The buildings and other accessories are Lemax. The figures are a mix, including Lionel. After several experiments, I found the following technique works for me. The tree armatures are dried goldenrod. I spray paint them with a heavy coat of flat black from a rattle can. (Cheap is good!) Then I sprinkle yellow, orange , and red on the wet paint in that order. Try yellow on one side, orange in the middle, and red on the last side. Stick the wet and foamed tree on a piece of styrofoam and allow to dry. Plant said tree on the layout. Don't worry about what falls off and lays underneath the tree. It will look very natural.
Chris
LVHR