I too use woodland scenics plaster cloth. I agree - it's easy to cut, hardly any mess and it conforms to the shape of the framework structure. My layout is small so I might changs my mind if I had a lot to do.
Micro Mark also sells a tool called 90 degree punch which I love for windows. It's #81652 and sells for 22.95. Worth it's weight in gold. I chuck it in my drill press. Works on basswood or styrene.
I think my interest in logging started in the Adirondak Mtns. in north eastern New York State. I spend a lot of time there. There is a museum called the Blue Mountain Lake Museum. They have a lot of space didicated to logging in the northeast. Got a lot of information there. On a subsequent trip...
I don't think I'd pay $50 for that car - it's too modern for me as well. But I can see having a few of them around gathered over time. It truly is beautiful. It's far better than my attempts at weathering.
Have you tried a product called Sculptamold? It's a clay like product that dries in the oven. I've used it for rock work and it's quite good. You can do all your carving while it's soft. It dosn't shrink and it's available in colors. If you get a wall you really like, make a mold and reproduce...