I use Eileen's Tacky Glue. A thin layer along each strip seems to work well. The sub-roofs on each building are styrene. On the Passenger Depot, I painted the corners and the bottom; I should have painted the whole works a dark color. On the Freight, I painted the perimeter red, but the field is black, much better.
The Passenger Depot is the -20 series shingle, a darker black. The Freight Depot is the -14 series shingle. An issue we have found with full size sheet goods (plywood, MDF and even paper) is that the color of one side is different from the obverse. The shingle batches for the Passenger Depot were all quite uniform, but I started into a new sheet on the Freight Depot today and it was a slightly different color than the previous shingles, and I think this was due to using either a different batch of paper, or placing the paper other-side-up in the copier/ laser cutter. This is more obvious in color (Jim!) than in the posted view.
At the recommendation of another contributor, I will provide a wash of pan pastels to even everything out. I already tried this on the Freight Depot and it worked nicely.
Now...to wait for some decal film from MicroScale. I was hoping this would come in late last week, but not so.
As with trees, the effect seems to be reinforced when you stick to a single technique/ brand. I have a Banta Silverton depot (a stand-in for the D&RGW Leadville Depot) with the paper shingles. These are thin and small, and I did not seem to use enough adhesive. When I recover a bit from the Freight Depot, I am considering redoing the D&RGW roof with Wild West shingles. Even in a different color, I think it will be an improvement. Trouble is, these models eat up shingles to the tune of about six sheets per building. Ka-ching!
I painted the wall with what is my last bottle of the venerable Polly S Boxcar Red. Then I masked off the approximate outline of the sign and applied an uneven coat of Vallejo white, which I may have cut with a drop of grey. After a week, I gave the building a workout with my fiberglass eraser. The decal uses Mr. McKenzie's fine artwork laser copied onto MicroScale decal paper (I put a whole bunch of signs on a sheet, including multiple Freight House signs, one set stretched a bit). The decal was applied over the painted styrene and lots of Micro- setting solution applied. After about the 10th application I used a razor to cut the last bit of decal film to get it to settle around the battens.
I have some MicroScale stripes, but this may result in too white a stripe. I am pondering other solutions.