what is the best exercise to strengthen the lower trapezius and with what clients’ is this most helpful

I use an exercise that I call ‘Reverse Shrugs’. For guys who usually have longer arm length, I have them set on a bench with arm straight and slightly behind their bodies and instruct them to push the shoulder blades down. Since I have a dual axis cable tower, I do a similar exercise with individual loops hanging off the cable attachment. There the clients sits on a ball of bench and gets the same cue.