A variety of commercial tree and landscape materials have been used. PermaScene was used to sculpt ground level terrain around trackbed, streets and structures. Ground foam was used throughout the layout. I like them. Rail is flex track on cork bed.
All track is painted to look rusted.
Ballast is applied with diluted white glue. Model railroads are three dimensional art. There is no right way. Listen to all the good ideas but do what works for you. Decide how you want to spend your time.