Place the joint raker at the beginning of one of the creases in the wall where you desire to remove the mortar.
Begin to move the rake in one direction, pressing to remove as much mortar as you can in one swipe.
Remove the rake and insert it back in where you originally set it and repeat the fluid motion in that same area until you have removed the mortar to a depth of twice the width of the overall width of the wall.
Repeat this motion all over the entire wall, both horizontally and vertically, until you have removed all the mortar to an equal depth.
Remove any extra pieces of mortar around the joints using the soft paintbrush. Begin to repoint the wall if you desire.