I have been known to use wadded up towels under my ground cloth for hills. You can achieve some nice diorama effects that way. But I do find it a fairly labor intensive process to get everything just right.
Last weekend I went out and got some larger containers of green and brown acrylic paint and a stippling sponge to experiment on my yoga mat. Now, if it would just warm up in my workspace!
Self taught, persistently behind the times, never up to date. AKA ~ jeff
More verbosity: http://petiteguerre.blogspot.com/