Here's an account I wrote some time ago. It's one way of using a big camera for portraits:

Yesterday I shot six full face portraits with a Tachihara 810HD view camera and the process went smoothly because almost all the work had been done before the sitter arrived.

I used a stand-in subject seated in a posing chair to set exact focus. Then I ran a string ending in a small bead from the camera to the stand-in. String length was adjusted so that when the bead was between the subjects eyes and the string was taut the subjects eyes are in exact focus. Camera focus was then locked down because the string and bead would guarantee image focus and I would not have to look again at the ground glass or get under a focussing cloth.

Then I checked light meter readings, adjusted for bellows extension, set the aperture, the shutter speed, and cocked the shutter. Since the session was only going to take a few minutes and my sunny-day light wasn't going to change I would not have to meter again.

Next a film holder was put into the camera and the darkslide was pulled.

Finally the sitter arrived, took their place in the chair, did the bead and string routine, held their head still, dropped the bead, turned their eyes to the lens, and I fired the shutter with a long cable release.

The fastest portrait in photography comes from a preset view camera with a big sheet of film waiting in the darkness behind the lens - but only for the first shot!

After that there is a bit of work: changing film holders, cocking and firing the shutter, and bantering with the sitter until the end of the session. I'm in control because the string and bead delivers focus, the light is constant, the sitter's chair stops them wandering out of frame, and the long cable release lets me fire the shutter with my hand behind my back. The sitter doesn't know when to flinch.