Trap is a straight swing-through game. You simply come up from behind the target, right up it's wake (pretend it leaves a contrail like an airplane) and shoot as you pass. The follow through establishes the lead. This does have applications in the field.
I use different techniques at skeet depending on which target I'm shooting and which gun I'm playing with. I have only two actual 'skeet' guns, the others are all field guns of various weights and guages. When shooting field gun skeet, I score best with swing through. It requires minimum thought, and besides it's fun.
Last week I was able to demonstrate four techniques of shotgun shooting to a new shooter. On station five, I started with a sustained lead tracking ahead all across the field, then did the sweep through trick, an 'insertion' (pull away), and finally something called a 'collapsing lead' which a friend taught me after paying an instructor $200 to learn it. It involves intercepting the target from a vertical swing or from the opposite direction of the flight path. Very interesting to experiment with and useful on chandelles and battue targets. I imagine it might work pretty well on decoying ducks.
There is no 'correct' way. The only unchanging thing is that somehow you need to put your pattern where the target will BE, not where it IS.
