As I promised
Guy, I am back with a brief description of how I do ground cover. Note that this is just the way that I do it, others may do it differently and I don't claim that this is the best way.
I have a spray bottle of water/isopropyl alcohol mixture at 60:40. I also have a water/glue mix in a bottle of Elmer's White Glue, also mixed at 60:40 with a few drops of Dawn Liquid Dishwasher Liquid. Use White Glue or Glue All and not School Glue which is much more dilute.
First, I use Woodland Scenics Green Blend foam. I use it as a base for everything. Sometimes I add some Dark Green or Yellow to it for variety. Today I am just using it right out of the can so to speak. I actually transfer it to a small condiment cup from restaurant pick up orders for ease of handling; partially visible on the right of the above picture.
Next a brief shot of the target area between the two industries in my current project area.
First, that loose ballast was swept back to the spur where it will receive glue when I do the adjacent ground foam.
After tracing the building outlines, I wet the whole area with the water/IPA mixture. I took a picture, but you can't see any difference.
Then I spread the ground foam over the area, since this is between two industrial buildings, it is not spread as evenly as if it was a lawn.
That small area in the top right corner with the gravel leads to a stairway at the back of the Coffee Distributor.
After it is in place, I thoroughly wet it wet it with the water/IPA, holding the spray bottle at least 12" away to avoid scattering the foam.;
Then I use the glue bottle to dribble the water/glue mixture over everything. One could use an eyedropper to do this, but it is one more tool that has to be cleaned.
In the top of this picture, you can see that I spread some coarse foam closest to the tracks to represent a more rough and seldom mowed zone.
It looks sloppy right now, but the glue dries clear. At this stage, I can add more foam to any thin spots without any other treatment. In this case I added a few sprinkles of brownish foam to the surface. With this much glue, capillary action soaks the foam that you add. I generally wipe the rails with a paper towel to remove any water/IPA. This is not necessary but it kinda cleans the rails if needed.
This is what it looks like three hours later.
Any stray material can be removed with a single-edge razor blade after it dries. Any touch-up I usually do a day later. In this case some of the voids will be filled in with field grass or weeds; or more foam can be added if the bare spots bother you. Since this area is about 3.5' from eye level, it is not as critical to be perfect. I will see today when I look at it and return the buildings.
I hope that this is useful to anyone who has any apprehensions about ground cover. It's relatively easy, but can't be rushed. Practice in a far corner of the layout first.