A couple of tips can make it easier. First, angle your blind so it's pointed to the right (if you're right-handed) of where the ducks will land. The easiest shot from a lying down position is about 20 degrees to the left. You can swing a long way to the left but not so well to the right before you bind up. Second, don't rush. Ducks aren't looking at you--they're focused on the decoys. You can't dawdle, but you can take the time to be as smooth as is feasibly possible when you're trying to sit up, mount the gun, and shoot in a tippy coffin blind.