looking for guidance on how to sand or prep the surface of the shell’s wire stitches I can’t pull out. I thought I’d use a file, just thought I’d ask before I try.
If you have a pair of fine-tipped diagonal cutter, or a pair of nail clippers, trim the wires flush with the wood. This way you avoit tears and rips in the sandpaper. A file might be too aggressive.
You can pull some of those wires out, from the other side, by heating up the wire with a Heat Gun. Be careful not to scorch the wood! Maybe use a piece of aluminum scrap as a backplate or something. The more you get all those wires out, the better the hull will look.