Hi Matt:
Like another poster said, the "paint chip" phenomenon in model finishing doesn't go well with OD painted US equipment, historically. (Frankly, I'm not sure it goes so great w/dunkegelb German equipment either but that's another thread!)
US OD paint had great adhesion properties, I'm told. If there was a scratch, it'd go down to the bare metal. For weathering purposes, have a read on this great article:
http://www.missing-lynx.com/rare_world/rw03.htmShowing wear through layers of accumulated dust looks more realistic to me than tons of dark brown scratches and splotches.