Well, obviously you can't get any darker than black, so a wash won't have any effect. What I usually do is paint the parts a very dark gray. That way, a black wash will add a bit of contrast. Then I would follow up with some dry-brushing with progressively lighter shades of dark gray. Honestly, I don't know how dry brushing would look over your coat of future (I've never coated an interior with a gloss coat). After the dry-brushing I paint the details like bezels, knobs, switches, instrument faces, etc.
You might try what I call a "heavy" dry brushing with very dark gray. What I mean by heavy is that the brush is not not quite as dry as usual when dry brushing. If you do it right, the paint will lay down everywhere except for the recesses, which will have the same effect as a wash. But again, I've never done any dry-brushing over a gloss coat, so I'm not sure if that would look good.
Hope that helps!
Chris