Started doing them with a barbell and static holds. We used to just work on getting our strength up.
I now use a hammer Strength shrug machine for all the work I do....and that is more than enough.
It is one body part that if I trained it any more than I do, it would grow out of proportion. I had to stop training traps when I was riding my motorcycle because it was hindering how high I could hold my head up on the bike.