The suggestion for 3-4 minutes per shooter is from my experience with all day big matches. The math might need to be different for a small club match. The main thing is that the times per squad are the same to prevent back ups.
When my wife and I run a stage, we put all the score sheets on a clipboard, fanned out so everybody's name can be seen at a glance. That way shooters can keep track of where they are. We also call out who is the shooter, who is on deck, and who is in the hole.