My name is Jeroen Sibia, I spent two years as a Business Analyst at McKinsey in London 2011-12 before joining Barclays Capital. I was from a completely non-target university and but sailed through the case studies with my own self-taught framework which I am happy to share with you.
Mock interviewing is without doubt the most efficient way to prepare for case interviews. You can do as many hours as you like reading MBA case books, watching videos online, and listening to podcasts, but you will not be at a level to win offers at MBB consulting firms until you do mock case interviews.
Trying to learn case interviewing by watching videos is like trying to become a professional football player by watching it on TV.