propper technique on shoulder dislocations

Hi I want to know, when doing a shoulder dislocation, lets say the basic overgrip when standing, should I focus on the arms doing the force upwards and keep any other force at a minimum? I have this doubt because pavel in his books said that one should try to "rip" the bar appart trying to separate the hands from each other as we pull back. SO, only upwards or upwards and "rip"? 

It's going to happen either way when you reach your sticking point.

Doing dislocates on a bar that doesn't move?  You either have the flexibility and strength or you don't.  

If you are asking how to do it then you don't so keep stretching and strengthening your shoulders.