You cut shoots or leaves? I think you are confused as to the different parts of the plant. The internodes are where the secondary branches meet the main stem (or any secondary branch off a stem). The petioles are the "leaf stems". The petioles connect the leaves to branches, often at internodes.
The growth tips, or "shoots" are the tops of the branches. This is where new leaves, branches, nodes and flowering sites come from. Cutting the shoots is not defoliation, it is pruning. Cutting the tops closest to the light during flowering is a bad idea as these would be the best producing areas. Pruning the lower, shaded branches (shoots, leaves and all) is done to remove areas that wouldnt produce dense, quality buds so the plant can focus energy on the upper tops.
When you defoliate you remove the mature, large fan leaves that shade out growth tips lower on the plant. Grab the base of the petiole with your thumb and finger and lightly jerk it downward. It should pop off easily and cleanly. Leaving a portion of the petiole is unnecessary and is more prone to infection.
I defoliate during veg and flower. I just started using this technique last run and I had better yields and not a single airy, immature bud on any plant. I pull fans that are blocking bud sites every time I check on the plants. Maybe a handful off each plat each time. I wouldnt go stripping all of them at once.
