In this video of the videoHow to Build a Surfboard, I show what I use to seal an EPS surfboard blank. Then show the process on how to seal the blank.\rbr\rbrLePage Big Hole filler is what I like to use because its light and pure white in color but you can use any type of spackling wall repairfiller and paint it to the color you like with water based paints. You dont need to seal a polyurethane blank or XPS Foam.\rbr\rbrThere are two angles filmed, one from my head and the other from a fixed camera. The fixed camera view starts at the 17:13 minute mark.