Woodland Scenics makes a product called "Flex Paste," which is a rubberized material intended to be used as a waterproof seal base for model water features (lakes, rivers, etc) to prevent leakage of the model water material, and also to prevent possible bubbles from the "de-gassing" of foam, if the modeler uses that as a foundation material under the water feature. It also has other modeling uses, such as simulating snowcover on buildings, terrain, etc.
Now, there's a company called Flex Seal that also makes a product called "Flex Paste," which is available at any hardware/home improvement store. Is it the same thing?
I tend to assume it is, but a WS product video shows that their Flex Paste can be sanded after it dries, while the Flex Seal's Flex Paste says on its product webpage that it cannot be sanded.
I'm planning to model a reservoir on my layout and would like to use Flex Paste as a base over extruded styrofoam. I'd like it to be flat in texture so the ability to sand it would be ideal for me.