For dishing a wheel (centering it between the dropouts), flipping the wheel over occasionally works for me.
My Minoura is old enough I don't have the red arms, and have to center the gauge by turning knobs to adjust the screws. I tried to get those gauges centered a few times, and then figured I could work on the wheels using one side at a time until I was really close to finished.
How do you adjust the short red arms for different width rims? Can they be independently adjusted?