Split the lifters into two or three flights, and then have them declare what their openers are. Arrange each flight so that the lifters are in order from weakest to strongest by there openers. After each lifter goes have them declare their next attempt. Each lifter in each flight should be given three attempts before starting the next flight. While they are going make sure you have dedicated side spotters and judges.
Who ever pushed the most weight wins, or split it into weight classes and figure out who wins each class.