Here are a few pictures of the ballasting job I did on my past layout and my current one.
Current layout has WS coarse cinders glued to a Styrofoam substrate. TABLE top is 1/2 inch MDF, 3/4 inch Styrofoam, then a top layer of 1/4 inch Styrofoam cut out to inset the tracks. This makes the tracks appear like they are sunk into the ground and also you use less ballast.
These 2 photos are of my previous layout. If you live near a menards, they sell a 50 lb bag of blasting sand. It's an abrasive grit for stripping paint and rust from metal. I bought a bag for $7.99 less my 11% rebate. 1 bag could cover several large layouts (a bag fills a 5 gallon bucket ).