This can be conducted just like the first round of the World Cup. Setup a gaming session with 6 players. Then pair off into 3 games running simultaneously each playing the same co-op level. That way the timing should match up and there will be less waiting for others to finish. After every round, trade partners until you have all played 5 games. You can all agree to play the same level over and over, or decide to progress through the co-op campaign playing the first 5 levels.