shooting primer

What valspar primer are you using? (I spray Valspar DTM all the time and have never had any issues with it)
are you mixing it correctly (correct activator and reducer)? are you waiting for the primer to "flash off" before you spray another coat?

when you clean the surface prior to spraying use two rags, one wet one dry, wipe the surface with the wet one then wipe it dry with the other. don't try to wipe the whole car down at once, do a fender then a door etc..

You might have better luck with a different brand of wax and grease remover.

If you still have problems it could be something airborne. Prefilters (where ever air is entering your spray area) are a important to keep your spray area clean of airborne contaminents.