Patrick, I hate to say this, but I have to agree with Mark and the others. I absolutely loathe Tamiya acrylics for brush painting and since I invariably have to touch up my airbrush work with a brush at some point, I've quit using them altogether. I am sure, however, that someone here will come up with a solution for you. That said, your doing a fantastic job so far.
Cheers,
Bud