Advice on spraying white enamel

Rough vs runny is not a color issue. It is just that white highlights roughness or runs.  It is likely the problem is one of several issues: thinning ratio, distance from model, or pressure.  Further, these are related.  Changing the thinner ratio can be compensated for by adjusting distance.  I personally use 15 psi for gloss paints, 20 for flats.  I know people who use other pressures but find many airbrush novices start too high.

The primary problem that is truly a white paint issue is coverage. Yellow is even worse.  I find I have to use more coats or a thicker coat with these- also a good primer is almost essential with these colors.

I find that when I need to apply white as a color I start with a base of flat white first. The flat white acts as a good primer base for the gloss. Once the flat white has cured I apply the gloss in several light coats until I have the consistency of coverage and gloss effect I want.

Many light coats...

A good primer, wet sanding and many light coats. White and yellow are killer colors to paint. I use Tamiya AS-12 Aircraft Silver as a primer and then, like Gerald, use Flat White as my first coat. Thin lots and put on lots of very light coats.

Thanks for the advice guys. I'm going to start with flat white thinned about 50% (Testors airbrush thinner)then a lot of coats of insignia white. I usually spray at between 10 and 20 psi. I'll post the results in the aircraft forum.

i totally agree! i hate spraying yellow N white.