The final step before polyester primer is to fill pin holes in the body work. At this point, all the filler should be thoroughly sanded with 150 or 120 grit. Blow the filler out very good with a blow gun. Make sure every square inch of filler is blown out.
How to fill the pin holes? Glaze or filler needs to be a certain thickness in order to dry properly. A small film of it will not dry, and will stay gummy. Not only is this a challenge to sand, the glaze also hasn't dried properly. I always first make sure glaze is squeezed tightly into the pinhole, and then make sure there is just a little bit of glaze over the top of it. It doesn't take much, but just enough to be able to dry, and sand nicely. Here's a picture :
It is very tempting to fill the pinhole, and leave just a film of glaze. It is also important that the glaze actually dries. So a little more than a film is required.
••Once the glaze is completely dry, sand with a small, hard acrylic sanding block with either 120 or 150 grit
I really like the U-POL Dolphin glaze.