For Jon O.

I flew in primer for 50 hours.  The only advise I have come across is to "clean surface with scotch brite and cleanser before sanding with 320 grit."

In my case, I used an D/A sander with 80 grit followed by 220 grit on palm sander with a final hand sand with 320 grit.  Im happy with the results.

Regards,  Bill Hogarty

PS  My primer was made by US Paint for marine use