I use 'g' for the group effect. I think it needs to be setup individually.
Set 1 attack normally.
Hit and hold the 'g' key.
Click on the ground (on or ) near a different unit and then drag your mouse across the sectors which you wish to clone to. You just have to touch the sectors and not cover them completely. You want to drag from the forward troops to the back ones since the order in which the group dynamic hits each sector is the order in which they will move.