Talking with two event promoters, they indicated that the staff you get invariably prove challenging... Their recommendations:

  1. Send the staff a copy of the program, map of the facility, and an explicit description of what they'll be doing. Tell them they'll be tested on it.
  2. Have them show up two hours before the show opens, walk them through the show, and then test them.
  3. During the show, make sure you check in on each one to see how they are doing, questions, etc.

Things I'd try:
Meet with facilities management as soon as possible. Make sure you have facilities on-hand for the show.
Everyone gets your cell phone number.
Give the staff the list of jobs ahead of time.
Ask them who wants to be leaders for the day.
Let them select which jobs they want when they show up. Leaders get first pick. Rock Paper Scissors for any ties.
Make the leaders escalation points, all questions go first to them, then to you.
Do as much as work ahead of time as possible.