Sikorsky are not going to write in a checklist "if the helicopter goes wildly out of control immediately switch off a hydraulic system, and if that doesn't work, switch off the other one". This is what I would do if faced with this situation.
I had an excellent Training Captain during my conversion, in ground school, I was taught to turn off each hyd system in turn if I ever experienced any hint of control issues. I was also taught the importance of the after start / pre flight hyd check. But that was a long time ago.