I've not tried this technique myself, but I've seen it done on a video on the net somewhere. Pre-shade with black/dark grey, then when that's dry, AB the panels, leaving as much of the edges of panels free of paint as you can. Then mist over the whole area to tone down the difference between the pre-shade and the centres of the panels. When you're satisfied with the finish, stop there! Takes a bit of practice I imagine, but worth a try if your'e having problems.
Of course, if you're doing a multi-tone upper, you'll need to mask off ALL sections, and won't be able to do the "first coat all over" thing, as you'll obliterate the pre-shading for the other colors. Upside is that you save paint!