Hi Josh,
My advice is to forget about drybrushing.
You could shade some of the darker, recessed areas with grey or a grey/blue mix, then do a light wash.
I'm working on an M20, admittedly in wartime service, so I wanted dirt in the interior, but I used very dilute washes of raw umber applied along the joins and panel lines. I kept the wash in crevices and along seams, and avoided getting the white too dirty on first application. I suppose if you're committed to dry-brushing, you could hit the high spots with white after doing the wash and shading.
Andy