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