My advice is to read up on porting basics.
Procedures, techniques, fundamentals, etc.
Get a junk head similar to what you’ll be working on, and practice on that first.
Strive for consistent shapes and sizing, and don’t worry about the flow.
I ran mid/low-11’s 33 years ago with mild ported 906’s that were never flowed.
Later on, after I owned a flow bench and had the heads off for some updating.......they finally got tested.
Only flowed about 240....... still made 500hp with a hyd cam.