I am going to contradict the course foam thing that course foam is roughoy a minimun of 1/8 inch on the average... think about it how many blades of grass or dirt are 6" in diameter?
start with a nice medium brown / tan flat interior paint, then sprinkle varieties of ground foam dependent upon what you are modeling; dark brown for farm land with bits or rows of green foliage. lighter tan base with a light to medium green for lawns, light tan for forest cover. that will give you your basic color.. follow that with random courser foam but don't over do. avoid those big clumps of foiliage.. they just destroy the scale of what you are doing and to me they look bulky and well clumpy! if you do this while the paint is wet you will need very little glue and if you do need additional adhesive use diluted matte medium and spray with a light soap and water solution to set the foliage and get teh matte medium to flow..
