Well... that's what I call a wash, NoMercyJoe. You wash the figure in a dark paint color (I personally like burnt umber - between brown and black) and wipe away the excess. The paint will stay in the grooves and otherwise stain the surface of the figure. Sometimes you need to do this 3 - 5 times to get the best look, and you might just glob paint into deep crevices and barely wipe it away...
Drybrushing is dipping the end of your brush in paint, then drying it almost completely by running it over a paper towel briskly. You then have a mostly dry brush, but there's still some paint there. You (also briskly) dust the figure with the bristles (and I use a longer-bristled brush for this) and the paint will be deposited only on rough or high areas. Smooth areas will usually stay relatively clean.
One of these techniques gets paint into grooves, nooks and crannies (washing) and the other gets paint onto raised surfaces. I tend to think of washing as dirt and drybrishing as multiple scratch and wear damage.
I would suggest, Phruby, that you wash Cody with a flat color that matches the general tone of the ground on the planet you think Cody was last on... Tatooine would be a reddish brown, a forest planet would be a dark, earthy brown and/or black, and a more alien planer presents a whole other set of issues
. Then I would choose a dark, flat gray, pewter, or maybe silver and dry brush the raised areas on the shin, the armor strap on the foot, the thighs near the knee, the shoulderpads (heavily), the chest, and the forearm gauntlets. Dry brushing should be subtle, though. Even heavy drybrushing to show damage has to be somewhat subtle.
For more prominent paint defects (deflected debris), you might - before you wash the figure - scratch a small divot in an armor surface, fill the divot with silver paint, then lightly coat that base with a flat black, allowing some of the silver to show through. After you wash the figure, it should look like a nice, old dent.
Phew... I need to get back to work. I can't wait to see how you finish (abuse) Cody