After getting the ballast and dirt in the yard, I started adding the ground foam base.
I used an Earth blend starting at the edge of the dirt and ballast and spread it outward, followed by fine burnt grass over top of that leaving a bit of the earth blend showing. Then I came back over top of the burnt grass with a turf mix.
While this looks ok, I plan to come back and add a layer of static grass over all of this to give a look of tall weeds. I also plan to glue down some shorter static grass within the yard, both between the tracks and hopefully between some of the rails in a random pattern. We'll see how this works out?
And for the fun of it, I roughly edited the last photo to give me an idea of the finished product. The large brown area is reserved for and industrial line that will serve a string of large buildings similar to a downtown theme, someday...