Great high tech, low cost idea. I will have to try this in N scale.
Just barely dust the truck frames with flat brown primer. Don’t entirely coat them, let a little of the black show through. The heightened realism is astounding. You really don’t need to paint the wheels, they don’t really show much. I don’t bother doing it. You may want to. On black cars like tank cars, I use gray. Just enough to lighten the frames so the light picks out the details.
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