Gregsn, I am in a similar position to yourself, in that I am working on a Do217K, which has a black underside, with RLM 76 uppers.
Having looked at numerous photos of this camo scheme on the real thing, one thing is clear, there are many shades of black, or should that be grey? As Dgarrington points out, I was therefore looking to pre-shade all the panel lines in black, then apply different shades of very dark grey to each panel.
I know it sounds time consuming, but having looked at the real thing, even neighbouring panels were differing shades! I was then going to finish off with a black/dark brown sludge wash.
Look forward to seeing the finished article.
Karl