Hi Gary.

Sorry I'm late to the party, but I got held-up by a computer malfunction.
The building in the photo, the silo loading track at GERN, was put in place before the ballast was glued down, although the building was not fastened to the layout. I used a paper cup to dump the ballast/ground cover between the columns, spread it with a 1/2"-3/4" brush, then did the tap-tap-tappity thing with the brush handle. Since there's nothing in the way other than the columns, I was able to use my "wet water" sprayer from various angles to soak the area, then applied glue with my dropper bottle.
This part of the facility wasn't in place at the time (even though it's supposed to be the older part of the complex

).
The track between the buildings was done with the "older" structure in place.
As was the track by the loading dock.
This helps to keep the buildings from moving around should a massive derailment occur,

but still allows for removal, in case I ever get around to installing the second level of the layout. One of the support brackets will require that the entire main structure along the backdrop will need to be removed and part of the roof modified to clear the bracket.
I don't worry about getting "wet" water on the buildings, as it has no effect on the styrene unless they're very dusty: "mud" weathering on a roof is generally not very convincing.
Wayne