FWIW, I don’t use Oxiclean on Vulcanized stems. Results in an orange peel finish that just takes that much more work to sand smooth.
Drilling an appropriate size hole in a block of scrap wood and securing in a vice, I scrape off the oxidation using a sharpened piece of steel, or even a utility blade. Then I sand it by applying mineral oil and strips of 220 or 320 3M Flexible sandpaper. Usually only takes 15 minutes or so, then I might work up a few grades or just take it to the wheel. But that’s just me...