I like Vallejo Primers as well. If you are going to be using acrylic paints, a primer really helps the paint bite. I thin them with Vallejo’s proprietary acrylic thinner and add a drop or two of flow improver. I spray in thin dusting coats until the desired coverage is achieved. The primer is dry to the touch in minutes. It is not cured though as this process (for me at least) takes 24-48 hours relative to humidity (summers where I am in the American South can be brutally humid and thus extend curing times for acrylic paints). Depending on your airbrush setup and spray method you may experience tip dry. When this happens to me, I simply clean the tip of the airbrush with a soft brush moistened with Vallejo Airbrush Cleaner, spray the excess off, and return to spraying the model.