The fastest way to coach a rep is also the least useful one.
You watch the call. You see the problem in the first minute. So in the debrief you say it: "Next time, open with the patient type."
The rep nods. The next call improves a little. And the month after, the same rep is waiting for you to fix the next call.
Most of us learned to debrief this way. It feels efficient.
What changed my debriefs was one habit: ask before you tell.
"How do you think the opening landed with her?"
Then stay quiet.
- When I tell, I do the thinking and the rep takes away my answer for one doctor on one day.
- When I ask, the rep does the thinking and takes away a way of looking at any call.
Whitmore built GROW on this idea. Michael Bungay Stanier puts it simply in The Coaching Habit: stay curious a little longer, and give advice a little more slowly.
Two warnings from my own practice.
A leading question is still telling. "Don't you think you should have..." fools nobody.
And asking does not mean never telling. If the rep could not see it, say it. Just ask first.
“Tell, and the rep learns your answer. Ask, and the rep learns to find one.”

Lesson 2 of 23 in Step 4: Coaching, with the full guide and a checklist for this week.