318 head porting for the average joe

Justin I need some clarifying since I don't know where to begin. I'll run the 2.02/1.60 valves that I already have. Should I cut the new seats before starting any porting or I can cut them later? My plan is to start polishing the chambers and then cut the seats, so I wont run the risk of scratch or damage them.

I ordered an electric grinder, some stones and a standard abrasives porting kit.