RE: Lapping valves on 4 stroke
Brasso or Silvo (brass or Silver polish), followed by a really good clean. Don,t get any on the valve guides though.
I've tried gripping the stem in my dremel, it worked for me, but I wouldn't recommend it.
Do you guys have pencils with a small rubber (eraser?) on the end of them? I CA that on to the valve and twist it between my palms, lift and rotate a few degrees, repeat.
I have to agree that a good clean is probably all that will be required though.
Dave H