[YodasLuke]

The left arm could more or less be a string. For all of us that have suffered through the trials of being told that "the left arm does all the work", it's a hard transition.
The way that I've learned the feeling of the left arm's role is simple. I start at impact fix (hitting), and I try to stretch a DEAD left arm with my right. I start my practice session by picking up my left arm with my right forearm and then pushing it back down. I'll make as big a motion as possible without gaining left arm involvement.
Most of the left elbow pain that I've seen is the result of rigidly trying to keep the left arm straight or by trying to lock it.

One of the biggest myths in golf:
Keep the left arm straight. (Left arm idea)

One of the biggest truths in golf:
Make the left arm straight. (Right arm idea)