Dave,
I have quite a few Downtown Deco buildings.
(I also have the Barber Shop not shown.)
I built these 25 years ago with little talent in painting, airbrushing, constructing little buildings or working in fine detail. In short, I was walking into this blind. But I religiously followed the excellent, detailed, step-by-step DD instructions. The end result was so gratifying for me!
To jog my memory, I just looked at some of the DD instructions which I saved. They instruct you to put the walls together first. No problem at all. Just follow their instructions.
"If I can do it, so can you!"