I wait until my plants are in flower before I supercrop. I supercrop by squeezing a growing shoot that is taller than the other shoots. I pinch with my index and thumb until I hear a snap, at which point the growth shoot falls over and the inside of the stem feels squishy. In 3 days, the limp growing shoot will right itself back up and start growing towards the light.
EDIT: In the mean time, the growth from the branches below the bent over stem increases which creates a more robust and even canopy.