How to Prime ?

I use a spray can to prime,  I dont use my airbrush to prime.  I find it to hard to keep the connector cap and the plastic tube and all that perfectly clean to not screw up my white.

If your shake your rattle can enough, it will thin out.  Also, soak the bottom part in hot water, that helps as well.

I primer with rattle-cans... Wal-mart brand enamel primer, 'bout a buck and half a can.. Works for metal, plastic, resin, wood, just about everything...  Doesn't matter what you're gonna paint over it with as long as it's dry... Drying time on the primer is about 15-40 minutes, depending on heat & humidity...

I always prefer airbrushing my primer coat. The rattle cans can be a little tricky. If you're not careful, you can apply too thick of a coat and run the risk of runs or "orange peel". Then, you're back to square one.

If you are using acrylic paint, you can use an acrylic OR enamel primer. If you are using enamels, use an enamel primer. The acrylic primers (white or gray) works well if you prep the model surface well and allow the primer to set up for a couple days. I would use a primer paint for the primer, not an actual color paint. The primer paint is a semi gloss instead of a flat. That way, the flat coat will adhere better and smoother. 

Andy