Practice. I wear mine fairly tight (and I am old & large) so doffing was a problem at first. With time an experience and a little technique, it is no longer a problem. Never had any success trying to chicken-wing my way out. I'm right handed. I unbuckle and push the left strap off my shoulder. I then reach back with my right hand, grab the bottom of the tank (single) and pull it to the right an up. This causes the left strap to loosen. Sometime it almost fals off and sometime it take a little shimmying. I then grab the right hand strap with the now free left hand and slid it on down, continuing to support the tank with my right hand. It's not pretty and may even bruise the upper right arm a bit, but it works for me. But it is prettier than what I have to do to get in it when I don't have enough room to go over my head with it.