Rails with light rusting:
- 1pt burnt umber
- 2pt burnt sienna
- 2-3pt water

Mountain rocks:
- base coat of dark or medium gray
- black wash
  1pt lamp black, 8-10pts water
  brush over entire surface, let run into cracks
- hightlights
  dry brush top corners with thunder gray
- optional: smash-brush with raw umber