Thanks guys for the input.
Some of the industries I have planned include a couple paper mills and a printing press, so I be been trying find out what kinds of commodities those facilities would use and what cars they would be transported in.
For the paper mills, you would need wood pulp going in and paper going out, of course. You'll also need clay slurry and chemicals to whiten the paper in particular for bond-type paper. Newsprint isn't quite as white as the bond paper, so the bleach wouldn't be needed, but the clay would be to give the paper a smooth surface.
For the printing company, you'll need a siding for boxcars. The rolls of paper are carried in the boxcars and are hauled out by a forklift. The rolls are huge, by the way. I saw this once on a press run a very long time ago. At the time, the paper was being delivered by truck, but the old siding was still in the back albeit all rusty with weeds coming out of it.
The printing company may or may not accept ink and cleaning materials via rail as well. The cleaners, such as press-wash, are petrol based and are really volatile. They also use lots of glue if they're are also a book binder. In those days, they used animal or cellulose glue. Today they use rubber cement. The printer may also accept in string in large quantities as well to stitch the books together on the binding machine. This could come in as spools loaded on boxcars.
For delivery of finished goods, look for old-fashioned 1920s - 1940s' style delivery trucks. They look similar to the older UPS trucks we see around. I was thinking that even in the early to mid-1940s, companies were still driving older vehicles because of the war times and the earlier Great Depression when no one purchased any new vehicles.
Hope this helps. I worked in the printing and graphics industry for about 5 years directly, then later for an equipment manufacturer.
John