Phil Heath said:
• usually he perform this exercise at the end of biceps workout (single exercise)
• is not so important weight of the dumbbell, but important is technique of this exercise
• need to focus on moving, do not throw the dumbbell, and to achieve the maximum contraction of biceps
Surely you have a question about the number of repetitions. He recommends choosing weight with that you can make at least 12 repetitions.
Notice how Phil Heath turns the brush, and doing a little pause at the top of lifting. It is also important not to put elbow on top of the thigh, and abut against the side.