First off is the car ready for paint?
With bondo dust over everything it sounds like it needs primed first.

The car should Be washed with Hot water and a mild soap then rinsed , then it should be wiped down with wax and grease remover,before any body work is done .
This helps insure that you dont have contamination problems down the road.
Your bondo work can also be wiped down with another wipe down of wax and grease remover before being primed. just blow it dry with your air hose. Then you can spray your primer .

SprayTech