Hard to say without knowing the tip size of your primer gun, and everybody sprays different so there's too many variables.
I usually shoot it with my sata 1.8 and wait 10-15 for the first coat to flash, better to make sure is completely satin looking dry. The next two coats about 10 -12 minutes.
I wouldn't mix more primer than what you can spray in 15-20 minutes.
2 or 3 coats depending how good your body work is and how much filling you need.
