There’s not just the control group micro, there are actually another two good ways to micro them. A) Idle the monks, and nothing else. Then use the “select idle military unit” hotkey to quickly cycle between them and give targets. And B) Select the whole group, choose a target, hold control, click on one of the monk icons to deselect it, and retask the remaining selected monks onto a new target. Repeat as fast as possible until all monks have a target.
You may also want to star Arena, and learn an FC monk build.