Vallejo airbrush primer, what am I missing?

Alright, so. I have been trying to use this airbrush of mine in order to prime some minis to paint (Votann counts-as, for those of you that care) and I have been spraying some parts to try and figure out why in the world this isn't working. I have used the black air primer before and it's worked fantastically. Nise and smooth and great coverage. But gray (image) and ivory have been this splotchy affair. And the white is even worse. Those three are unthinned as I read it was unnecessary and from the Mecha color line. It doesn't cover very well and leaves these strange standy things on the test objects. I have been using a small pocket sized air compressor I got off Amazon that adversities 15 psi but it's probably less.

So I have come for help from the veterans. I'd love to just use the black but I use contrast paints for effects like leather. What am I doing wrong? Or should I base black, spray a light color then pick up the bushes? I just don't want to buy anything else untill I have the right information.