I seem to remember an article (don't ask me where) that I read when I first started thinking seriously about building a layout. It used faux fur, but instead of gluing the entire mat down, what they did was to pour a plaster base or use the plaster on hillsides etc. Then while the plaster was still wet they pressed the faux fur into it. When the plaster had completely dried they pulled up the cloth and strands of the fur that were embedded in the plaster pulled lose from the backing, leaving strands of irregular lengths to simulate natural grassland. They emphasized using very cheap faux fur so that the strands would easily pull lose. If you died the plaster an earth color before laying it I believe that this could be another interesting way of using faux fur for grasses.