"Strip the knurling."
That's what Dave Tate told me when he coached my bench press two years ago when I first visited the Elitefts compound in Ohio. It's a simple cue: you're just imagining that you are trying to strip the knurling off the bar using the J-hooks of the bench as you unrack. The goal is to keep the lats and scapula tight during that portion of the lift.
I'm ashamed to say that it's taken me almost two years to really get the hang of this cue, and I haven't quite mastered it yet. That's partly because of my poor kinesthetic awareness, and partly because I was missing one piece of the puzzle: even while "scraping the rack," I wasn't keeping my shoulders tight.
Here's a summary of my problem, from a writeup with Dave two years ago:
At nearly every meet I’ve ever done, I’ve gotten slow start commands on the bench press because my unrack is a little wacky — I protract my shoulders to get the bar out, and then reset them, and with all that shit going on up top, I don’t pay much mind to my elbows and squeezing my triceps so that it’s obvious they’re locked before I begin the lift. (They are locked; I couldn’t hang out at the top otherwise, but it’s hard to tell.)
Scraping the rack alone wasn't enough to correct this issue. I also had to learn to unrack using my elbows, not my shoulders. (It's actually quite like in the squat: if you try to unrack using your hips, you're going to have a difficult time maintaining a neutral spine and strong brace, so it's often better to unrack using your knees.)
Once I started unracking by locking the elbows, not protracting my scapula, my elbows naturally fell into a better position and I had more strength at lockout.
If you're struggling with shoulder pain or a weak bench lockout despite strong triceps, give this cue a shot and see if it helps!