As a surfer, it's inevitable for accidental bumps and collisions to create dings, damage, and cracks to your precious surfboard. It's important to learn how to properly repair surfboards to ensure you won't miss out on any upcoming swells or be left land locked during a trip.
Varial Foam is very easy to repair and requires no special treatment. Varial is closed cell, so if any water enters the ding during your session, you can quickly evaporate it by placing the board out in the sun for 30 to 60 minutes. From there, you can repair it the same exact way that you would any other surfboard with polyester or epoxy resin.
Polyurethane Foam or even worse, EPS Foam will take hours to even days to fully evaporate any water that was absorbed like a sponge. Heat from the sun can promote delaminations. If you repair your surfboard with any water remaining in the ding, it will gas out, form an air bubble/delaminate and potentially ruin your board.
This is a video on how to quickly and effectively repair any kind of surfboard: Varial, Polyurethane, or EPS/Epoxy: