thePup said..
Roy - would you consider giving us a bit of a demo (of course without compromising your trade that is brother!!) of your skills ???? I would love to see just a glimpse of your showcase is why I ask ..... cheers !
I have a few videos of fin foiling but they don't show any special technique. I just foil in the direction of the water flow with a hand sanding block, and it takes a very long time. The trick is to constantly check that there's a proper foil section with no flat spots in the middle. It's time, care, and elbow grease rather than any trade secret, anyone can do it.
For a glass fin with a box tab I'd also use a bastard file to get the area where the tab meets the fin base. That's the hardest bit to get right.