Dear Dan,
Just as a practice trick, make MUCH bigger backstrokes than usual and allow the momentum of the downstroke to gather a full head of steam thru the bottom of the stroke and help propel the lead shoulder up in a flowing manner. Then as you back off this overblown backstroke back to something closer to your normal backstroke, retain the feeling of the momentum of the putter coming down from the top of the backstroke. You want to TIME the swing thru the bottom so that the putter moves the lead shoulder up out of the way, OR you clear the lead shoulder out of the way of the oncoming stroke so the lead shoulder does not get in the way.
If you instead "pull" the stroke and putter head thru the bottom and up into the follow-thru, it's highly likely you will do so with a lead shoulder yanking everything on an arc to the inside thru and past impact, which is a pull or at least a cut stroke. The lead shoulder should always be working vertically up from the balls of the lead foot thru impact, at least for a modest distance past the bottom of the stroke (about 3-5 inches).
You only have to accomplish this dynamic for 3-5 inches past the bottom of the stroke thru impact.
Cheers!
Geoff Mangum
Putting Coach and Theorist
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