i feel like i hit my traps hard on shoulder days just from shoulder exercises. i do heavy weight upright rows and and do negatives for my traps, it burns! then at the end of my shoulder routine i like to do behind the back smith shrugs, stepping out from the bar and doing heavy, slow shrugs, 3-4 sets of 15. finish with a lighter weight dumbell shrugs for high reps. kills em!