Trainman 2001....
I don't remember who posted a thread here but it dealt with creating a two toned ballast effect and if I remember correctly he used black spray paint on grey ballast so it was a gray and a mixture of light and darker black.
you could do same using a brown spray paint and accomplish two items at same time.
all he did I believe is hold spray can 12" above ballast and misted it slightly until he acieived his desired effect might be worth trying.
$oo