I've gained considerable length. I'm almost exactly 15 yards longer with all my irons and a little more with the driver. Making the swing shorter and starting down slower makes sense for hitting it longer, right? That's why instructors have job security.
I have just started to try hitting and these, for me, are the hardest things to make yourself do:-
Throw all instinct out the window.
Stop the backstroke early.
Sense the lag.
Lean on that clubshaft with heavy heavy hands...steadily...positively...evenly until the ball is well gone.......well well gone.