Fiberglass sanding / primer filler
ALL raw fiberglass parts should be completely sanded with 80 grit paper with no remaining mold "smooth" parts. Molded FG parts will all have mold release contaminants. You need to have a rough surface for your primer-filler to grip to, otherwise, you are just asking for paint delamination down the road. Throughly clean/wipe down to remove ALL dust.
The best way to fill pinholes with primer-filler is to spray on the primer, then squeege the primer back and forth on the surface for the first coat, to work the primer INTO the holes. Otherwise, the primer covers the hole, not filling it... when you sand down the primer, the holes will still be there.
Dry sand first coat of primer with 220 grit, respray then wetsand with 400 grit. Don't use that red laquer spotting putty for filling "large" defecits, it shrinks too much and can delam over time.