One of the biggest breakthroughs my students have had with this is to make the switch from thinking of it as a 'pause', and replacing that idea with a 'hang'.
See, a pause can feel like a disruption. An interruption in your rhythm. You back swing, then just freeze for a while? There's just this void where you are doing nothing. People are telling themselves "Back, freeze, swing". It's weird, at least it was for me. Furthermore it doesn't fix the problem of jamming your cue forward too quickly. Just as important as a relaxed back stroke is a very smooth start to the swing. Half of the people I've seen with a pause in their game come back slow, pause, then jerk their cue forward.
I fill the void. I am not doing nothing. I am "hanging". Like when you are on a swing-set and you float up, then there is that moment where you feel like you are perfectly weightless. Then you start moving down, slow for a moment and then picking up speed and accelerating all the way through the middle of the swing motion. On a swing set you don't actually pause. You are constantly accelerating. But it sure feels like it. So that's how I picture this: "Back, hang-creep-swing!" I come back easy, hang, let it start to creep, then let it pick up speed through the cue ball.
A great example of this is a draw shot that Chris Melling hit on me at the DCC.
The shot is at 19:14. What's really cool is going frame by frame using the '<' and '>' keys. If you look at the moment the cue tip strikes the cue ball (frame during 19:15) and then arrow back you can see the cue stick took 17 frames from impact to when it started moving forward from his bridge hand, then there were four frames where the cue stick wasn't moving at all. So:
4 frame pause
10 frames for the cue stick to break the initial inertia and move infinitesimally to the rail (one inch)
5 frames for the cue to creep about three more inches
The last 2 frames for the cue to zoome the remaining 8" and swing through the cue ball!
8/9 of the time was only 1/3 of the movement!!! I think this is really illustrative of a good swing.
In recap, the pause should be a natural hang at the top of the swing, and it's not nearly as important as not rushing the forward stroke and letting the cue stick accelerate without a big burst of force, but rather with a slow steady increase that builds through impact. Not all pros pause, but all pros have a soft acceleration with good timing that starts easy and goes through the cue ball.