Several coats are required to cover the primer especialy if the paint is a bright color.
I find that with the paint I reduce the paint with a little reducer. ( not a lot ) Also I usally spray my paint at a higher tip pressure than what the directions call for.
Funny thing I suppose. I usally spray at the sound it makes when spraying and I do not look at the pressure gaauge.
Also a nice wide spray patern. Light even coats and more coats work out well for me.
I started spraying years ago and learned by trial and error. So my word may not be as the book reads.