Every time I go to the dentist I think about porting heads.
For my 302 heads I wore earplugs and a dust mask. The Sears electric die grinder came with a long cylindrical stone so I used that. It quickly wore down to a flame shape. I spent most of the time in the bowls, opening up around the valve guide and smoothing transitions. The pushrod pinch I was leery of but I did trim it some, and I got the port faces out to nearly 360 size, paying more attention to which side of the port was more important. I think it took about 8 hours. Being outside and use of earplugs makes it better.
You are right, going over the job the next day, one sees all sorts of little problems.
Congratulations on giving it a try!
R.