We emphasize in class that you are going to fight (or respond to an attack) in the same manner that you train. With that in mind it is absolutely imperative that you learn to hold and feed the focus mitts in a way that give both the holder and the hitter effective feedback. Also, the holder should be presenting a realistic target and offensive platform to deliver strikes from and to receive strikes from the hitter. Learning to become a good holder takes a long time but develops skills that will carry over into the hitter-role as well.
Following is a video of Chuck Liddell demonstrating focus mitt training with one of his many coaches:
