Used mine as a polisher this morning! I have a really cheap grinder, poss even B+Q.
Keith is right about long sessions - the motor on mine gets really hot, so I do have to rest it from time to time.
Big and small diameter mops have different value. I have one smaller one - about 3-4 inches diameter, with a lot of sisal (rough string) in it. Used with a relatively abrasive wax, it will work on really poor surfaces. The bigger and softer mops, used with a less 'cutting' wax have more subtlety.
This morning I was making scrapers for heat-stripping an antique skirting board moulding - shaped to match the specific bits of profile - from 1/16" thick stamped plate washers. Because they gum up so easily they need to be polished but still to keep a relatively sharp edge. The small wheel would take off the superficial rust and put a shine on the surface really well.
I've marked the position of the grub screw on the spindle adaptor with red paint so you can see where it is when the thing is running. It's not your knuckles so much as wrecking whatever it is you're trying to polish. Same goes for the pointy end of the conical thread for the mops - DAMHIK.
Oh, and use eye (and glasses!) protection every time and overalls. A lot of fluff/lint comes off the mops, and it's both waxy and gritty. It gets bloomin everywhere.
E.