Laying down ballast is fairly easy with no obstuctions yet. I have been making my own ballast now for some time. Using an old wheat grinder I take small rocks from various places and make it the size I want. I use a mix of white glue with water. I use a ratio of about 60/40, more water for thinner glue. I pre-wet the ballast, then apply the glue.
These ballast rocks are from the Durango, Colorado area scooped up from a slide area on the way to Silverton along the highway.