Hey Chad,
WWWHHHOOOAAA there, her's another suggestion/idea......
First off, paint the upper areas a shade of Russian green that you want. Paint the lower areas (wheeel, sides, and track) Schokoladenbraum. Give the whole thing a brunt umber or seina wash. Set aside to dry for three days or so.
Then, take Tamiya white, spray onto the top areas. Get a wide flat brush and a bit of alcohol (IPA for exmple) and brush here and there. More on the worn areas, less on the sides. Do not spray the Schoko. with white.
Give it a dark blue-ish wash with liberal amounts of raw seina or umber (fresh mud). Dry brush the lower areas shades of brown etc. Give it the perverbia scratches and chips that everyone likes, then enjoy!
Dave