All photographers will have their individual methods in portraiture, and it never hurt to experiment.
Incident: cheek in shade; cheek in shadow, front of face, add mid-tone (or grey card), average all — none of these specifically with aim-back (cone to camera).
If using mono film, meter should read in 0.5 to 1 stop increments. With tranny film (unlikely in this scenario), meter to 0.3 steps. You have a lot of latitude in mono and small adjustments generally will not have a lot of effect as opposed to printing versatility in the darkroom.
Spot metering will give any number of variations depending on what you are specifically aiming at, and 5° is too great an angle for spot.