I made my own car cards (with pictures) and 4 sided waybills, all using excel. It took a little trial and error to get the cards the size I wanted, then after that you just type in the car type, destination for each round and the spreadsheet does the rest. You can use these to create a switch list, or just figure it out in your head. I also eventually created a list of trains that would carry the various cars to different places on the layout. I have tried a few versions of the train list, with longer trains, then with more, smaller local trains. Longer trains proved to be more difficult to operate on the layout, so the smaller trains (max 10 cars) is my current favourite.
You then run some test sessions, keeping track of time, so you can figure out what the various "jobs" are in a session, in case you want to have more than one person running trains at a time.
Below is a picture of a car. I edit and resize the pictures so they are 150 pixels high. This ensures they fit properly on the excel spreadsheet car card sheet I designed.
I create a holder that can be attached to the train table at each siding. I use paper clips to attach the siding card holders to the layout skirt. You can attach permanently with glue, screws or pins, if your layout front allows for it. The cars in the siding card show what cars are on the siding at this time. You have to look at the waybill to determine if the cars need to be shipped, or have already been received for this session. The siding and train cards are printed on a thicker stock of paper, in a colour printer, with 2 cards fitting on an 8-1/2x11" sheet of paper.
Below is a sample train route. On the left is an overview of all the various trains and the train number, direction and what towns they pass by. On the right is a route schedule, showing the towns in order, the siding location, siding number & direction they face and what industries are on each siding. This helps plan what cars should go on each train. Some towns do not have a "run-around" track, so you have place the car on a train travelling in the correct direction, in order to make a "backup" switch move. This adds more complexity to an operating session, as you may have to deliver cars for various small towns to an intermediate town siding, where they will be shunted and placed on another train to get to their final destination.
Below on the left is a Train card, that has a number of car cards inserted into it, with a current waybill showing. On the right is the waybill (set to turn 2), which is placed in a car card. My car cards have a picture of the car, making it easy for visitors to identify each car visually. The design of the car cards print 3 cards on an 8-1/2"x11" piece of paper. The waybill goes into the car card, then the car cards are grouped and placed in another holder that represents the train. These holders are the same design as the siding card holders, just named differently. The waybill is printed double sided, 6 waybills per 8-1/2"x11" piece of paper. I have designed a tab in the spreadsheet for each 6 waybills, where you type in the car type, then the town, industry name and contents for each of the 4 cycles. The receiver in one cycle automatically becomes the shipper in the next cycle, so typing is minimised.
There are various books that describe the car-card system. I simplified the design a bit, and used a computer to print out the waybills. Some companies supply blank cards, and you fill them in by hand, which works the same. My switch list is created by placing the car cards into the Train card. You could also create an actual switch list, which I presently do not do. Either way, the switch list is used to create the train that goes from the start to the finish point. On my train card I list the order of the towns, so the train can be blocked to make switching at each town or siding industry more efficient.
You can start with something simple, created by hand. Then try it out for a few cars on a few trains. I have evolved my system considerably over the years. I am still trying to find a balance between simple, fun to operate and a design that can easily be picked up by a visitor.