Vince, welcome!
I've been meaning to try microbrushes, which are a plastic toothpick looking (actually, like the buds used to clean the ears) with a little ball of sponge(?) on the end. Their use is to put small bits of glue on models in inaccessible places.
For your scale dilemma, wondering if you could use them for your mottling? Folks without airbrushes have been using bits of sponge to achieve the effect since I had hair, which is a couple of weeks ago... Kennedy was in the White House.
I've always felt that a lot of mottling was done "in the field" without an airbrush, using whatever was handy, rags, brushes, branches- so that a "rough" rather than a "refined" result was the end result. That's my argument, there was a war on! Also, there was a lot of aircraft wastage and replacement, so op-tempo meant "get it painted" for the next sortie.
On some aircraft, the application differed from one side or section to the other,
depending on the artistic ability or penchant of the Grunt(s) doing it. When I was an enlisted peasant, we just wanted to get it done, and avoid the wrath of the Sergeant and the Lt.
I'm thinking a nice B of B ME-109, with hastily applied mottling over the hellblau sides would be a good trial. I'll report back.
