Pouring the Streets and Sidewalks.
Extensive testing of the track is essential before its covered with street paving. Especially that intersection. Making revisions to the track would be most difficult when its buried in plaster. Plus its fun to just run the cars around too!
It seems logical to me to pour the sidewalks first. I used angle stock that was the thickness I wanted the sidewalks to be. Where the sidewalks curve at the corners I cut slots in the angle stock so that it could bend (sorry about the dark photo). Then the angle stock is spiked down to create a trough to pour the plaster into.
I used lightweight hydrocal, but if I was to do it again, I would use Durhams water putty.
Originally designed for DC operation, the track is cut into electrical blocks. In the photo above you can see where the wires come up from under the layout and soldered onto each rail of each block. That also has to be tested for electrical continuity before being buried in the plaster.
Once the sidewalks were in and the track passed inspection, I started in on the streets. Stripwood equal to the height of the rails were glued against the sidewalks (where the gutter would be). Then plaster could be be poured in between. The stripwood and rail would be used as a guide for a paint scraper to smooth out the plaster. I stuffed thick string into the flangeways to keep the plaster out, but I think I could have just masked if off with tape.