I'll do my best to help here, but there are others who are no doubt more qualified.

First, my golf instructor also wants me to lead the downswing with a rotation of the hips. This is the method favored by Ben Hogan (see "The Modern Fundamentals of Golf"). This has been troubling for me too. I did find what I think is the missing link in David Leadbetter's DVD, "From Beginner to Winner".

Leadbetter also teaches his pupils to rotate their hips at the beginning of the downswing, but shows that this is accompanied by a weightshift from the backleg to the forward leg. In the video it looks like a little "pushoff" that leads to the hip rotation. I haven't had a chance to try this at the range yet, but it looks promising to me.

As for drills, I believe he recommends a half swing to build tempo and to ingrain the weight shift sequence. I'll look at the video again and repost if I've not got the drill correct.

Hope this helps.

Jim

Merry Christmas