Going "hand-in-hand" with the idea of finding the "slot" by making a "reverse loop" downswing, the golfer should fire the hips forward to get the required power. The feeling I have is that my right hip leads my arms into impact, while the arms make ZERO muscle movements once set at the top of the backswing (they simply fall and rotate out due to momentum of the lower body). Both butt cheeks should be visible from DTL at impact due to this hip rotation (most beginning golfers commit the error of returning the hips to the address position).
Another thought is to use is to think of the knees, which may cause less problems than concentrating on the hips. If the swing is driven from the ground up (as we've heard countless times), the knees should turn and drive towards the target first while the upper body stays back. The hips and everything else will follow in sequence. Consider the footage below of Rory McIlroy. Pay attention to his knees at the top of the backswing and then as he transitions into the downswing; the knees move around and towards the target first and everything else follows. This also helps keep his head behind the ball and prevents too early a weight shift.
All of the golfers that can hit the ball a long way have one thing in common. They are firing their hips around on the downswing. Another common fault I see in teaching is the student's hips not being open enough at impact. GolfTEC's motion analysis computer measures how many degrees the hips have turned open (towards the target) at the impact position.
Exaggerate the hip rotation for a fade and hold off the forearm rotation by tightening the grip.
Here are some swing thoughts that a handful of my students think of when trying to turn the hips more through impact.
"Fire the right hip around."
"Fire the right knee towards the left knee."
"Get my left leg straight and left hip turned behind me"
"Get my right pocket turned to the ball as soon as possible."
"Turn my belt buckle towards the target"
"Hit the ball with my right hip."
I call it "holding off the shot." I'm keeping my arms quiet with far less forearm rotation and delaying the closing of the clubface. I think of it as squaring the face with my body rotation. You can see here my hips have turned significantly toward the target before the club has reached the ball. That's a good fade feel for me.
Consider the images below of Mattero Mannasero and Jim Furyk. Both use a reversed loop downswing to hit from the inside, and look at how open their hips are at impact. The right hip clearly leads them into the ball, much like Ben Hogan's timeless swing.