Noticed the headset feeling a bit notchy, so deciding to clean it. Top is a cartridge bearing so no major issues.

Bottom is a sealed unit, but wondering can I take the black band off and clean or is it just a case of cleaning the outer shells and putting grease on to minimise any further issues?

Does any of that make sense?

Find where to get a new bearing, then remove the black band by gently levering it with a Stanley blade and a small blade screwdriver. Clean it out then refill with grease .If you mess it up or the bearing is too borked,then get a new one. 🙂