Just an FYI for anyone who didn't already know this, hopefully you can learn from my stupid mistake this week.
Tamiya metallic colors (blue in this case) airbrushes great. You might expect, after doing some detail painting by hand (in my case, blacking on a 300ZX T-top) that you could touch-up by hand brush with the metallic blue if you go over a bit doing the blacking.
Not so. My hand brushing pretty much ruined the car's paintjob because the $*%&ing metallic paint, even after being stirred for ten minutes, won't mix properly... at all...
Moral of the story: Don't ever, ever hand brush Tamiya metallic colors... don't be stupid like me.