I used some of those "bottle brush" Christmas trees - the ones with the bristles trapped in a twisted wire "trunk". I snipped off random hunks of bristles with scissors, then sprayed the trees with hairspray from a pump applicator. An application of coarse ground foam finished the job. Mine are supposed to represent cedars. Sorry I don't have any better pictures, but they
are supposed to be background trees.
They're the darker ones towards the rear of the photo:
This is the same area, from a different angle. The three straight out from the end of the track are a hunk of cushion foam - its peaks and pockets look somewhat like the papier mache "flats" for eggs. I brush-painted the white foam with dark green latex paint, then used hairspray to affix some ground foam.
The above view was taken with the camera on the layout - from normal viewing angles, the sameness of the "trees" is not apparent.
:-D
Wayne