Bare minimum - using a finer grit - the 320 as recommended.
It's too late now, but less is best. You really don't need a big toothly ripple for the paint to get a mechanical bond. On the other hand, ignore all advice here and believe and follow the directions of the manufacture.
PS. some of that doesn't look like bare fiberglass to me.
Last edited by chucklesR; 03-12-2008 at 10:13 AM.