I'm at the stage where I've finished expoxying the interior of the boat (a C16) and flipped the hull over to cut off the copper wire and sand.
First of all, read the old forum posts where they tell you to get a special trimmer to cut off the copper wire very close to the hull or to bend them back and forth until the wire breaks below the surface of the hull. Had I done either, my afternoon would have gone more smoothly...
Following the book and video, I cut the wire with my regular wire cutters leaving about 1/32"-1/16" of wire sticking out from the hull. Using 80 grit on my RO sander did take this off, but it wasn't leaving the hull flat and was also making indentations in the wood around the wire. I quickly stopped before doing too much damage to the hull (and initiating the Viking funeral!). The dense pad on the bottom of my (Dewalt) RO sander was allowing the paper to rise slightly over the harder copper and not sanding to a flat surface.
After taking a break, I came back and tried sanding by hand with a small block of wood and 150 grit paper. This worked much better. I'd start with light pressure and slowly sand the copper down to the wood increasing pressure as I took copper off. I'd hit 3-4 wire ends with a back and forth sweeping motion. I'd hear and feel a thump-thump-thump as the block passed over the wire that eventually faded to a consistent sanding sound as the copper became flush with the surface. This took off a lot more copper than wood and ended with a completely flat hull and no indentations.
My 2c worth for today.