tips for spraying primer

Solvent pop in primer isn't normally a major problem. You encounter it a lot more in color and clear coats. The major reasons for solvent pop is laying the material on too thick, then not allowing enough time before spraying on subsequent coats. If the solvents in the first coat don't have time to evaporate, then you lay on a second coat, the solvents from the original coat will burst out through the second coat, hense the name 'solvent pop'. You now have small craters at each place the solvents burst through.
Spraying in cooler temps means you should allow more time between coats, since it takes longer for the solvents to escape as the temps drop.