1. If you are shooting gloss white, a primer is imperative prior to your topcoat.
2. I've found that flat whites go on primed and unprimed surfaces better than glosses. They are also not as difficult to thin to get them through an airbrush.
3. Testors flat white enamel and Floquil Reefer White enamels are excellent. I've never had any trouble with either one.
4. If you're getting snow flakes, it would seem your paint is not thinned enough. Once properly thinned, and you decide not to try any of the ideas above, you might try spraying a little further back from the model, keep the brush moving, and realize that with a very thin white, it's gonna take several lightly misted coats to cover an area that otherwise would be done in one with a darker color paint.
5. As a last resort, you might try a plain old spray can of white. I built the Tamiya 1/32 F14 years ago, and used a spray can on the landing gear. Worked great. Krylon and Plasticoat are two brands that come to mind. You might even try Testors out of the can. Just remember: Spray from about 10-12 inches from the kit, keep the can moving, and don't try to cover the kit in one coat.
Hope this helps.
Gip Winecoff