You can use CM2 to find out if any railcars are set up to carry a commodity. Open CM2 and in the Search Action Panel pulldown, select Name and enter the name of the commodity of interest. CM2 will list kuids for it and if you right click on one and select View Dependent Assets you will see what industries and what railcars are set up for it. As an example if you Name grain hp you'll find that there are 2 hoppers that are set up to carry it and a Silo that holds it.