Try holding the pick just like this:JoeyParm wrote:Feel like the way I naturally hold the pick isn't conducive to this motion because of the way the pick is cutting across the string.

Between your thumb and middle finger - thumb slightly over the edge of the pick; index and pinky curled; wrist slightly bent downward; pick at a slight angle - between parallel and 45 degrees - and slightly leaning down toward the ground.
Here's another view:

Notice the wrist angle. I believe that Ed's wrist bends according to how he is holding the guitar at the time so he can get the pick in the right spot, but it's always at least slightly bent downward.
The most important part is the "so-so" motion you make with your hand and forearm. Maybe Ron could explain it better. He seems to have it down.
In all honesty, I just tried to copy Ed's motions as much as I possibly could when I first started playing and it just clicked for me. Here's a short video clip of me doing it without even thinking: