I'll go on record as saying you should have an experienced hand oversee or do the grinding. It is not an academic exercise—there is an art to it. Best to learn on a disposable engine like a Chevy. You can put too much sideways pressure on the stone and get the seat out concentric alignment with the guide. This is not readily apparent until the pre-assembly or checks with Prussian blue.(
https://www.motorcycleproject.com/text/vlvjob04.html)
If you choose grinding over cutting, you will make a lot of grit dust. It will go all over the engine. This stuff is ABRASIVE. Clean, clean, clean.
Russ