Are you aware of the command called Site Improvement Legend. While this does need to have a Site where you have applied Site Improvements to the surface, it does automatically create you the legend for just the Site Improvements that have been assigned, and it also lists the Material layers and the material thicknesses for each Site Improvement you placed.
While creating Site Improvements and Materials in the MSI Library takes a few minutes, the application of them to a surface does not require you to do the full takeoff - you can use the Assign Site Improvement command to place them, they then get color coded and flood filled directly and then you can run the Site Improvement Legend command to create the drawing legend in an automated way.
The benefit of using the SI approach is that the areas do not have to be closed polygons, you don't have to use track region to create them, and then assign properties to color them, so in reality the whole process should be faster than any other method, but you do need the Materials and Site Improvements defined in the MSI Library but that is reusable from project to project.