On doubles, do NOT watch the first bird break. Trust in The Force and go directly to the second. Do not waste valuable time on something that has already happened. Insert your left hand in front of the bird and fire. When the stock touches the face, the gun should fire.
Eyes are faster than hands.
Start the eyes where the bird is first clearly visible and the muzzle about half way out to where the target will break. You will be surprised at your vertical margin of error on teal if you have accurately taken the line of the target. To take a cresting teal, shoot the feet. Right handed shooters should shoot the right bird of a pair first so that both eyes can then be brought to bear on the left. A right handed shooter typically shoots to the left side of the bird and may want to hold a bit right to counteract this.