There are many ways, as you have already heard.
This is the method I used on my latest builds.
A mix of white glue, model R.R. ballast, Woodland Scenics turf, a glob of brown paint, and some hair clippings to represent grass caught in the mud.
Apply to the suspension and allow it to dry. Scrub some ground graphite onto it and then earth tone pastel chalks.
Happy Modelling and God Bless
Robert