Simllar method to those posted above. I brush on full strength Elmers white glue. Then sprinkle an even layer of ballast on with a teaspoon.
( Hats off to Keith, no way I'd ever find the patience to do inbetween the ties.)
I do plan to eventually weather between the rails/ties to tone down the plastic roadbed.
The next day I go back and wet the area with the 70% alcohol as Hotwater mentioned . Then I dribble on a 50/50 mix of water and white glue using and empty Elmers gue bottle which makes a great applicator.
I also painted my rails with a Woodland Scenics track painter pen "steel rail" TT4580.
