On the bushes, I formed them from the filler, spray painted them brown, sprayed them with spray adhesive, then threw them in a container of flock. Give them a shake, and you're done!
For the trees, I formed the filler onto the armitures, carefully sprayed each filler ball with brown spray paint, then the spray adhesive and sprinkeled Noch leaves onto them. The spray paint and adhesive hold the filler onto the trees.
I took some foamcore, stuck tooth picks into it a regular intervals, then glued them in with white glue.
Form up your bushes, stick them onto the tooth picks, then spraypaint. You can do around 50 at a time. You still need to individually spray each one with the adhesive and flock them. That's where the mess really is.