Mud covered track like one might see next to a grade crossing is simple to do even long after the track is down. As with my post on oil soaked track, I rubbed some fine dirt into the area with my fingers and worked it in further with a short bristled brush, in this case I used an old wallpaper smoothing brush that had very stiff bristles that broke down any remaining large particles and embedded the dirt solidly into the surfaces.
I followed up with the usual spray of denatured alcohol and diluted glue and while everything was still wet, I sifted on more very fine dirt and rubbed that in to produce the slick mud effects. I’m happy with the results seen here. The dark areas are still wet and will likely remain darker even when thoroughly dry.