The bases are then painted with thinned brown paint. I use Americana Dark Chocolate. The key is to thin the paint enough that it flows into the ballast/sand mixture without having to paint every tiny bit. The result is even coverage with a minimum of work/time.
Next step (above) is a lighter drybrush of the next lighter earth shade, in this case for me - Americana Driftwood.
Next step (above) is to thin some black paint and "blob" it onto rocks and coarser rough areas that I want to highlight in a grayish stone color. This isn't too precise...just blob black where it looks like you'll want the gray highlights.
Then a drybrush of dark gray onto the black areas - in this case Ceramcoat Hippo Gray.
Followed by a final gray highlight of Apple Barrel Dolphin Gray.
The base colors are now done, and all that remains is to add some vegetation texture.
While I'm sure that there are plenty of commercial products to use for grass clumps, I use my old stand by of cutting short sections of jute twine (packaging string, essentially) and gluing it to the stands. I use 2 or 3 clumps per stand. Just put a blob of yellow glue on the stand where you want the tall grass and then stick the jute into the blob. Then just splay out the ends to make it look more like a grass clump...I just use the back end of an old paint brush to press against the jute clump.
The above photo shows the stands with all steps complete except for the final application and highlight of dark green static grass. I just use a small plastic sculpting spatula and smear yellow glue where I want the green grass to appear.
Once the glue has dried, I brush the static grass areas briskly with a small stippling brush to "wake up" the static grass fibers and dislodge the loose fragments. I then finish off the static grass areas with a drybrush of yellow to highlight and give a bit more texture. Another photo below for a further example....
And that's it! It's pretty easy to do, and it adds a lot more texture than a simple flock will. The colors are my personal choice; you can select any combination that fits your terrain better.