This has loads of great advice in here. For me, greater time under tension, caused by holding the positive when contracted, and lowering slowly, using DBS to prevent shoulder protraction which can happen when shrugging with barbells, works great. I barely train traps any more. I never found the need for worry, once I realised what I wrote above, and the suggestions Dolce made, work so well.
Obviously he can answer for himself, but here is what Christian has written in the past specifically oriented towards the goal of increasing size in the shoulder girdle, relative to other body parts: http://www.T-Nation.com/free_online_article/sports_body_training_performance_interviews/20_pounds_of_hollywood_muscle
(scroll down to beneath the picture of Sebastian Cossette and click 'HERE')
I don't know if he'd want to revise it? But it is an explicit and clear framework for doing what was advised: 'train them 2-3 times per week with various movements'. Good luck mate