Improper mixing of the TotalBoat TotalFair Part A (resin) and Part B (hardener) components can introduce lots of tiny air bubbles, which form pinholes in the fairing compound as it cures. Any tiny pinholes will be visible when sanding cured TotalFair. When mixing TotalFair, blend the blue and yellow components together slowly and thoroughly; if you mix too quickly or aggressively, air bubbles can get trapped in the mixture.
How to remove pinholes
One way to get rid of pinholes in the cured surface, is to mix up another batch of TotalFair and use a plastic spreader or putty knife to force the putty into the pinholes, filling them. Alternatively, if you plan to paint over the faired surface, you can fill the pinholes by applying a high-build epoxy primer, such as TotalBoat 2-Part Epoxy Primer.