OB, I have my answer, thanks again! Kevin, how's the left-handed golf going?

IMHO, they aren't separate. I would go even further and suggest they work in concert with the right shoulder working down plane. This move is basically "uncoiling".

I would suggest this isn't something best learned through intellect, but by appealing to the body to show the way. In this case, by appealing to your baseball swing. (Hopefully, you played some ball as a child)

With a very slight raising of your left heel, "step" into a pitch repeatedly, in a "start down waggle" fashion. (Of course, in a Baseball swing this all happens on a horizontal plane.) Notice how the hips slide and rotation work in concert with the right shoulder moving forward?

Gradually incline your "start down waggle" toward the ground and you'll get the picture.

Hope that helps!