Re multiple industry new
I spent much of today trying to figure this out and got it to work. I agree make sure you are on the session layer.
1. Decide what commodity you want to ship. In my case, palletized bags of flour to ship from a rural flour mill to a big city bakery.
2. Pick the appropriate type of rail car (in my case, a flat car-a boxcar is probably more prototypical but I can't see the load in transit) and see if it can load that commodity. Some cars load no commodities, some load many on the list. Say you are loading flour palletized on a flatcar- click on the railcar and set a starting amount and make sure you can see some of that commodity on the car. If so, you know you have a capable car and can reset the initial quantity to 0.
3. Now go to the multiple industry new and set up that commodity in the "queue", (I also deleted all the other queues to make thing simpler), but then just as important, go to "tracks" and select the same commodity to load. At the receiving point, do the same but set the track to unload. I have not gone beyond one commodity per multiple industry, but I actually got a flatcar to load pallets of flour at the multiple industry new at the flour mill and unload at the bakery. Do not consider this as a tutorial since I barely know what I am doing, but as any experienced Trainzer will tell you, trial and error and this forum usually gets you through it.