I doubt prolonged mild exfoliation will do anything for the crud I and others have had. It just doesn’t reach deep enough.
Hydroquinone didn’t do anything for me.
When evaluating the efficacy of whatever protocol you’re using, keep in mind that in some cases, maybe most, discoloration resolves with time. If improvement is to be had from the tincture of time, applying Dr. Quack’s Penis Whitening Lotion daily likely won’t accomplish much.
“Improvement” is subjective. Skin tone of shaft skin is so variable that you can fool yourself into thinking discoloration is fading. Lotions or potions applied may slightly irritate the skin or otherwise cause a mild degree of flushing that camouflages the discoloration.