Build up your upper trap (trapezius) muscles faster with dumbbell shrugs. I see many exercisers doing incorrect technique with shrugs. Don't roll your shoulders when shrugging upward. Doing so will put pressure on your cervical spine. And, this is not the most effective way to do the shrug exercise (dumbbell or barbell).
The upper traps will be worked best by raising your shoulders straight up and down. Also, keep your arms as straight as possible throughout the movement and don't jut your head forward.
Make sure you also work your middle traps, lower traps and serratus anterior muscles (finger-like muscles on side of rib cage just under armpits) to keep muscular balance and avoid injuries. You must keep your shoulder girdle stable or you are headed for painful injuries!
The upper traps, lower traps and serratus anterior work together to allow you to raise your arms overhead (upward rotation).
Work your middle and lower traps with exercises like upright rows and cable rows. Work the serratus anterior with exercises like ab ball rollouts , dumbbell pullovers or medicine ball/cable diagonal chops.