With the Venessa machine, and on my plane, I will level the horizontal stab with a level. But that is because my plane is set up for 0-0 incidence, meaning when the horizontal stab is level, so is the wing. However, the wing is curved, so it is much harder to find level for it.
Then, the laser or plumbbob will point at the current cg. One would add weight fore or aft to move the cg into the recommended range.
I will balance my low wing killer bee upright using this machine.