A valve grinding tool for #4 exhaust?

[Sculldog1]

7 of 8 valves and seats lapped and ready to go back in! However, the #4 exhaust valve was badly pitted and I ordered new one. Question is is there a tool or grinding stone I might be able to use to create an acceptable surface on the seat as it is pretty rough? I will be lapping the new valve into the seat but thought that if I could use another tool to do some of the initial work it might go faster and give a better result.