I've never noticed a figure 8 movement when holding - I've seen side to side, up and down, but never a figure 8 when shooting offhand. Stance and hold dictates where most of the movement is. With the index finger of my left hand pointing down the barrel, but resting on the entry-pipe, I get very little side to side movement when holding, mostly just up and down. Not having to dope-out the side to side movement, helps with my offhand shooting, as it's easier to only have one movement. Trying to force a shape of movement by using arm and back muscles might work for some - not for me. Due to having a very bad back, I have to shoot rather quickly.
I stand facing the target, concentrate in it, bring the gun up and as the sights come in and settle on it, finish off the shot. Works for me.
Practice/shoot enough so you know what works for you.