With the spectrum ST4, it’s easy to control all 4 axis of motion at the same time. This video specifically demonstrates how to control your focus Fz axis.
The eMotimo spectrum st4 is a 4-axis motion controller with pan and tilt built in. It integrates and drives 2 additional powered axis like slide and focus. It is controlled by either the included wireless gaming remote, or the navigation joystick on the side of the unit.
More info: emotimo.com/spectrum