Looking good. Another way to do the mottle without an airbrush is to use a cotton bud (Q Tip), and I think the technique is described in the brush painting guide I posted some time ago. Here's a pic of a 1/48th '109E I built about 20 years ago, which was entirely brush painted, including the numerals and Gruppe bars, with the mottle done that way. OK, it's not brilliant, but the overall effect is acceptable, especially to the naked eye.