There are several ways you could set up a simple waybill system for your layout.
Make a car card for each car you have, noting it's type, roadname or reporting marks and number. Make a pocket on the car card that you can slip a waybill into.
Then make a bunch of waybills for your industries/car types. (If you have only the one industry that takes tank cars, all those waybills will be the same).
When you want to operate, you could grab for example up to 5 waybills (less or more depending on how big your layout is) at random and assign them to appropriate cars in your staging or interchange track. These can become your "inbounds".
Then you visit each industry setting off the inbounds and pulling the outbounds.
To make it so that you don't always pull all the cars that are already sitting at the industry, you could add a note to that "side" of the waybill along the lines of "Hold 2 days (sessions) for loading/unloading".
When you start a switching session, go through the waybills for the cars at each industry and either turn them to the next step, or add some sort of marker (like a paperclip) to indicate that it's been sitting there for one session already (if you want it to stay). Then select your inbounds and have fun.
If you have that one track designated as a clean-out track, that can make things interesting for boxcar operation. You could have the first move on the waybill as empty to the cleanout track, and then empty to the team track or pallet factory for loading, then outbound loaded. Or a loaded boxcar could come directly to the team track for unloading, and then outbound empty. Or even, inbound to team track loaded; to cleanout track, to pallet factory, outbound loaded. This could really add quite a bit of variety to your switching operations.
If you end up having more cars to spot at an industry than will fit in the proper track, the extra car can be parked on a runaround or empty track nearby to be placed the next time the town is switched, when room opens up for it. This is referred to as being "off-spot" and the car can be switched next session. (The real railroad term I believe is "constructively placed")