Weathering soft parts can be easy as can be. Get an old spray bottle. Fill it about half way to 3/4 full of warm water. Add black acrylic paint, maybe some brown acrylic. You're shooting for the color of motor oil that is burnt and hasn't been changed in a year or three. Try to imagine the last time you broke down and changed the oil in your girlfriend's Honda.
Shake it up real good. Wet your soft parts down with clean water and let them air dry to almost dry. Then hose them down with the burnt Honda oil mixture. Concentrate on the shin calf areas and get everywhere else.
Doing it this way looks a little better than just dragging it across the garage because it gets into the material better this way. Use black pastels or markers to add some streaks and marks in there too.
Good luck!
