Thank you for the writeup, I'll try to answer your questions the best I can...
What kind of high build primer are you using?
ProForm 2K Urethane Primer Surfacer PF 656C
Are you mixing it according to directions?
The first application I used it as high build, the second time I added reducer as per the manufacturers instructions to use as a sealer
What temperature are you spraying at?
-When I sprayed it was about 20 C / 68 F
Is it spraying too dry?
-Yes, even when I used reducer with it.
What gun and tip do you have?
Are you waiting between coats?
-It went on so thick I only laid one coat.
It is not a good idea to add more reducer to get it to flow. This can lead to a too thick build and solvent popping.
-I'm not sure that I added too much. the first time I sprayed I didn't add any and the surface was not smooth after spraying. Also, it takes a lot to sand down to a surface that is flat (not pitted).