Surfing School - Glassing - The Fill Coat
When the fins have been mounted (if using hard mounted fins), the board is ready to apply the fill coat using sanding or finish resin. Attach a strip of 1/2" tape along the entire edge of the rail flaring out at the bottom. Mix a quart of fast "hot" curing resin and using the paint brush, paint the top of the board. Hardening agent or wax should be added to ensure a sandable surface. Use the brush hairs with slight pressure to work the resin until you have a uniform coating and excess has been dripped off the taped edge. Pull this tape just after the resin begins to set.
When the first coating is hardened, flip the board over and repeat the process. Put the tape on the lower resined edge, just barely below the previous tape line. After painting the fins, make sure the excess resin hasn't accumulated at the fin base by only using a thin coat on the fins and working the resin in a downward manner to the tape line.