If you had a basic wall with a number of layers and the finish on one layer was say tiles. You could set this to be an instance parameter while the remainder of the layers would all be by type.
You could then specify in say bathroom 1 the tile layer is blue tiles material and in bathroom 2 the tile layer is green....
This would probably aid in better scheduling rather then just using the paint to to replace the surface while section remains the same is the currently set material and/or creating the exact same wall type just to specify the material change
