Based on recommendations from members of the S-scale Yahoo mailing list, I bought several sheets of Plastruct "HO-scale, 1:100" red brick, part #PS-97. The individual bricks come out to just about exact S-scale. Neither "HO" nor "1:100" is correct in their labeling. The extreme close-up below shows the S-scale ruler next to the sheet. I didn't quite line up the ruler with a single brick, but if you imagine moving it over a bit, you'll find that a brick is 9" or just slightly under that. My prototype measurement of a red brick is 8.75", so this is just about as close as you're going to get. Same thing with regard to the thickness of the brick. My prototype brick measured 2.75", and so does this Plastruct sheet; it is just a hair under three scale inches in S-scale.
I had done some extensive calculations to determine the size of the structure. However, when I found out that the Plastruct bricks are an exact scale version of the real thing, I decided to build the walls just by counting the number of bricks seen in the prototype photos. The Plastruct sheet material is only about 0.020" thick, so I decided to cut a mosaic and glue the individual pieces to a sheet of 0.015" white styrene. Additional re-enforcements of the wall section will need to be done later, but this allows me to cut up the sections of the wall and then assemble them around the spaces for the doors and windows. The right-most wall section, presumably the passenger waiting area, is the first wall I am building. It has a door in the middle flanked by two windows.
There is a grey-brick ledge under the windows, which I made out of styrene strips. On the left side, I fabricated the strips and then cut them at a 45-degree inside angle (against which another wall be mounted later). On the right-hand side, the ledge wraps around the side of the building (which I won't model).
I made the ledge out of four pieces of strip styrene, which is what the prototype looked like (as least from the photos I have). The top strip was a scale 4"x6" strip (with the 6" side horizontal and the 4" side vertical). Under that I glued successively smaller strips, namely 1"x4", 1"x3", and 1"x2" strips. This is a close-up photo of the ledge.
The space between the bricks and the actual window is filled in with 0.020" styrene. This is tedious work, especially considering I have to do this a number of times. I did the two side pieces (with all the odd cut-outs), and then one piece over top of both of them, so there are three pieces of styrene used here.
I then did the same thing to the window on the other side. I used the back of the Exacto blade to mark the stone cut lines you see in the prototype. These will be highlighted in the future using weathering powders.
The door area gets the same two side pieces of styrene. Note that I had to make a correction in the upper brick area (compare it against the photo above). The top section of the door area is more difficult because it has a curve to it. I determined the top of the curve by counting bricks down from the top of the door area. I made two pencil marks. I then used a thin strip of styrene and carefully positioned its "legs" up against the existing styrene. I put some metal weights on it to hold it in place. As you can see in the photo below, the top of the curve is nicely rounded, but that doesn't match the curve of the prototype door area. I used another metal weight and pushed it up against the top of the styrene strip to squash it down until the weight was even with the two pencil marks. I could then draw a pencil line around the styrene strip (which is not easy to do).
Of course, then the issue became, "well, how do I transfer that curve to a piece of styrene?" I couldn't solve that, so I cut a piece of the styrene to fit the rectangular area above the door, and then carefully re-laid the styrene strip over top of it. I did the same thing I described above and then marked the curve on the styrene piece.
Then it was just a matter of cutting and filing away the styrene up to the line. I am not an artist, so I can't quite get this perfect, but the curve is close enough. I then used the back of the knife blade and carved the cut lines as shown in the prototype photo, before gluing it in place.