Got my close-up ground cover technique down: 1. foam roller brush on matte medium onto brown dyed fabric or direct set surface. 2. Dust with mulch (to the scale you need; sifted fine for micro scale or big chunks for macro), 3. Repeat once or twice more over that until coverage/scale desired is reached. 4. Then sit down like a fool and hand glue down stuff that's on the ground naturally, like leaves, berries, twigs, pebbles, rocks, etc.
The idea of making these cloth ground surfaces like the sand, grass, and dirt is very versatile. If I need a bit of set in a background, I can use any old things around, boxes or old drop cloths, to make a base and then throw one of the texture cloths over the top for an instant portable place.