That's why I posted the Pic. I would love to hear from Jimmy or Tony Miller or somone that know's about these vintage ducks. Mine feels like glass, just as you described yours. You don't want to go too far. Think of it like your removing the clear coat from your car without hitting the paint.
After your done, and you apply the Neetsfoot oil, allow it to penetrate overnight before you do a second coat. It may take a week of applying and drying....