Thanks, Bjorgg. after some trial and error,lI have found that scraping is easier. the powerwasher did not have enough oomph to fully flesh the skins. it was 3100psi and I had a rotating turbo nozzle. My method is this: nail tail end to a curved wooden beam with a groove down the middle. Scrape with dull drawknife and dull small hatchet head. wash and rinse. tack out to dry flesh side up. clean off oils with rag and acetone. The beam is about 6 feet long and propped up on a wall, so I can do it standing up. The groove in the beam (sometimes) allows the scutes to sit down in it, making scraping this delicate area easier.
It may have worked better if I had done it the same day the fish were caught.