The dressed stone grinder will work OK but with cutters look for minimum 5 blades like some Neway types - or else you risk chatter and poor contact faces when trying the valve on them. Possibly you could get these Indian or Chinese brazed multi blade cutters to produce a reasonable finish, and anyway, most likely the valves get lapped with grinding paste for checking the seal.
The Hunger manual seat cutter has a 45 degree automatic feed head, 30 degrees available, so I do not need any lapping after that. The accuracy cannot be bettered with any other system and is extremely adaptive for very small valves and big ones the same. You do all correction angles to set seat width from top and in the channel too.
We had a set of seat cutters from China recently that has single cutters with all angles finishground in the single blade, same type of blades like with SERDI machines. That works quite well, provided the jig is mounted as it should and with a few turns on the handle you are almost ready to go, not much grinding in the valve is needed. In the link below there is a video clip showing the operation. But then, this does not help much in this thread , but in case someone is looking for that type of workshop equipment I can recommend this set for motorcycle jobs.
Vic
Link to Aliexpress:
Valve Seat cutter