Hold one side in an isometric contraction while the other arm moves through a dynamic (concentric and eccentric) movement. You then switch sides.
This simple modification not only helps you to create a new training stimulus, it also creates muscular overload by increasing the time under tension (TUT). By increasing TUT, you increase metabolic stress, a key mechanisms for growth.
The best cue is to keep your shoulder blades back and down. The first few reps show the incorrect position. In the last few reps, the shoulder are back and down.
Mike Mahler knows a lot of training bad asses but he thinks they're complete pushovers in their personal life. They avoid risk and couldn't make a tough decision if their lives depended on it. He wants to change that.