Looking at the shot you provided I'd say you are off to a decent start.
When working with my RB in situations like that I really like using an incident meter and monopod (or a tripod spread really narrow).
One click and I can set the lens, no guessing or math in my head. When I walk back to the camera position I can count steps and use the scale on the bellows extension to get focus close then a quick fine adjustment to focus with the finder and I'm ready to shoot. I assume the Pentax has a distance focus scale too.
The real trick though is to have practiced your routine well enough that you can carry on a normal conversation about your subjects work, their day, and the weather with them while you are setting up.