Here is a post from Yoda's site about Harvey Penick's slow motion waggle drill. Matthew quoting Penick.
"Originally posted by Harvey Penick:
THE SLOW-MOTION DRILL is a drill yuou can do at home and it takes much patience and many repetitions, but the time you spnd at it will pay off on the golf course.
Mickey Wright practiced this drill often. As an all-purpose drill that is good for whatever ails your golf swing, this is probably the best. You can do it indoors, so you can do it in bad weather or at night.
When I say slow mtion, I mean really slow, slow motion. If you think you are doing it in slow motion, do it even slower.
Swing the club very slowly to the top of the backswing. Always keep your eye on the blade of grass or the pattern in the carpet that represnts the golf ball; watching the clubhead go back is a terrible habit you can accidentally pick up in this drill and take to the course with you.
As you read the top of the backswing, replace your left heel solidly on the ground and at the same time bring your right elbow in close to your body. Very, very slowly.
Bring the club down in extreme slow motion about one third of the way toward the ball. Then stop a moment and hold it and feel it.
Now start again from your holding position and do it again-swing slowly to the top, lplant the left heel, bring the right elbow close to the body and stop about one third of the way toward the ball.
Do this four times in a row. Don[t get impatient and speed up. Very slowly is the key. After four repetitions, go ahead and make the full swing at last- still in very slow motion-into a high finish with the elbows out front and your coming up slowly as if to watch a good shot. Hold the pose. Feel it.
Now do the whole thing again and and again and again.
What is happening is that your golfing brian and your muscles are learning to start your downswing by planting your weight and moving your lower body to the left and you are coming to the ball from inside with your hands quiet, trailing and still cocked, not leading and spending energy.
Your golfing brain and your muscles learn just as well from repeating the swing in slow motion as from whapping awayon the range. In fact, it can be higher quality learning because no mistakes are bing made in the slow-motion swing...."
And Yoda's comment:
"This is the Downstroke Waggle of 3-F-5. In my opinion, it is far and away the best (if not the only) cure for that genetic deformity of the Golf Stroke --the Flat Downstroke Shoulder Turn (and its resulting 'Outside-In' Path of the Hands) [10-13-B #3]."
I don't know if Yoda was referring to 3-F-5 or Penick's drill when he said "...it is far away the best(if not only) cure..."