Because I’m a nice guy, I’ll tell you EXACTLY why I said to start with the valve job.
Because thats where the most power is. Because it establishes the throat size. Because it is the biggest factor in how the rest of the port is shaped.
I’m all for working the guide but for the amount of time and effort spent the most power to be had is in the valve job. You’ll get very little in return working the guide boss (although I suggest you do do it, just not at first) compared to getting the valve job correct.