They want to pick his brains to find out what he is doing right.
We all had time to pick the staff members' brains.
I go up to old guys and pick their brains.
Everyone on this ship wants to pick your brain, not later, but now.
"He'd pick my brain trying to see how the investigation was going."
And in so doing, you allowed him to pick your brains.
He just didn't want her to hear him pick Gary's brain.
I had the impression that he just wanted to pick my brain.
I wanted to pick his brain about a couple of things.
Would have been useful to pick his brain some, but that's not the mission.
Idiome