I used to always do light to heavy for 5-6 sets with the heaviest weight being about 365. This always seemed to work well although it didn't give me huge traps, but they're decently big. After laying off from my gallbladder surgery, I was doing exercises like lateral flyes with 30-35lb dbs, and I was finding my traps sore the next day besides my shoulders. And damned if they didn't start growing bigger. So now I've been combining lateral flyes with my shrugs (done with a lighter weight for higher reps), and my traps are bigger and thicker than they've ever been in only 3 months. Kind of funny because all my collared shirts now sit higher, so the width of my shoulders and height of the traps pulls long sleeves up enough that the cuffs don't come down to my wrists anymore. I'm going to have to get some new shirts with longer sleeves.