It removes most of the oxidation - externally and internally without using sandpaper.Why bother with the Ibepen bath if you're going to sand it anyway? Does it soften the oxidized layer that needs to be removed?
I only use Micromesh pads on the stems after an IbepenDeoxidiser soak.
I'm challenged using sandpaper and Duane's (@Chasing Embers) lighter method. I've removed too much material using bleach and sandpaper with my first attempts at cleaning stems.