We too usually recruit one rotation at a time, but because most people are willing to teach it doesn't seem as onerous as we thought to ask them to commit to several four or five week "rotations" a year.

We spread out the recruiting among our "curriculum design team" (the people we pull together to create each Rotation on a Bible story)

Each design team member recruits a teacher for the workshop he or she is writing and gets availabilities from the teacher so that we can work out the schedule. I put together a "potential teacher" list of all the people who had taught in the past and all the people who had indicated to me that they might like to teach sometime. If I know their gifts or preferences, I put that by their name in parentheses also. (ex. art or drama)

Our biggest problem with recruiting one rotation at a time is teacher training, so I'd really like to get away from that. We could be having teacher trainings every month or so! WHEW! The very thought wears me out!  That's why I like the idea of having a workshop leader help the recruited teacher on the first week with the lesson in their four or five week Rotation.

My goal for this year is to be enough ahead in our planning that we can develop a better mentor-type training. Teachers who will teach the next rotation will come and observe at least one week in the workshop they are scheduled to teach one time. I'm hoping that will help.
Good luck!