Leading the Target—Sustained Lead
The three most common methods of leading targets at long distances are swing-through, sustained lead, and pull away.
This method is a little more challenging because it requires more experience. Point your shotgun ahead of a moving target as you swing with it. You estimate the length of the lead necessary to hit the target, maintain that lead as you swing with the target, fire, and continue the swing.
Point the shotgun at a moving target, and then slowly accelerate slightly ahead of the target. Fire, making sure to sustain the swing during and after the shot.