I used black poly fiber from MicroMark for the tree tops. I was intimidated at first, but it is very easy. A little messy, but not hard at all. You just pull the poly fiber apart and roll small pieces into balls about half the size of a golf ball, spray it with diluted Elmer's Glue, roll in flocking, and glue it to the layout. Then repeat 495 times. I used grass or turf in different colors from Scenic Express and Woodland Scenics. They both are very good products.
Art