I have learned not to say that a railroad never used. This proved true in Bill Rice-Johnson chief engineeer of the Connaquessing Valley Railroad about using red dog for ballast. Having lived in his area I said no and protypicaly the railroads didnot use red dog. However last night I went to a site about The Buffalo Creek and Gauley Railroad, an 18 mile railroad in W. Va. and they did use red dog for ballast. . Since you are free lancing I would say as chief enginner of the CVRR, it would be alright to use it. The color would even add to your layout.
The site www.buffalocreekandgauley.com is and excellant site. Lots of pictures, some maps and history.
Tom