the effect that you speak of comes with full developement of the biceps, there is no way to isolate the area you speak of. First of all we all have different insertion points for our bis that you cannot change. Worry about using heavy compound movements to train the bis with, and even equally important as that, be sure touse correct form while training and just put some time under your belt, they will come eventually. If all your sets are cheat sets, then you are taking the stress off the bicep during the movement, hence you will not see proper development, make sense?