Only fish skins I processed was a big lake run brown trout, I started to scale it but the scales would barely come off and in the process
the skin lost most of its color
After that I scraped it as clean as I could and stapled it to a piece of plywood skin side down. Let it dry for a few days then cut it free.
I used a piece of it laminated on leather for a sheath, before gluing I sanded it a bit.
Timo has a skin along for grass carp in the How To section.
I guess if the scales come off easy scale it carefully, scrap it clean of flesh and fat, wash it with Dawn and staple it to a board to dry