the thing to do is get your set-up and practice with a friend &C ..
kind of like a dry-run ...
have the person sit, do some sort of chit-chat as you focus and all that stuff
... have them pose ... and see how things work for you.
the hardest part of any portrait is making the person
not realize they are in front of a camera ( or maybe not )
and getting your "routine" down so you can focus their eyes ( or maybe not ),
notice everything as you lock your focus ...
then stand next to the camera and get them to do what you want , so they aren't fidgeting around while
you focus + refocus &C ...
what fstop are you hoping to shoot at ? you have a little bit of leeway
sometimes ... ( even wide open! )
to touch the sitter's nose ... you know, like 3rd grade picture day
and i agree the graflex slr is the ideal camera for portraits like this!