Auto body repair & detailing: Painting Fiberglass, rust holes, pin holes

Question
I had to repair some rust holes on the edge of my rear fender well.  I decided to use fiberglass, it looks great and now I'm ready to paint.

How do I prepare the surface for painting?  I've heard from some that I should put on a thin coat of Bondo, others say just sand smooth and put on layers of primer until any pinholes are filled.

What do you think?

Answer
Just fill any pin holes in the fiber glass with spot putty and let dry and sand smooth, repeat if necessary until most of the pin holes are out. Then fill the rest with primer. If you fill them all with primer, the primer could dye back leaving the pin hole after it is painted and drying out. Spot putty is very thin and you can fill just the pin holes if you spread it thin enough.
             Thank you for the question!
             Ken