I guess for those not familiar with the 3-umpire system, reading a book and watching a video is only good enough to make you start thinking about it. The ONLY way to learn this system is to work it with knowledgeable partners multiple times.
Used to have umpires volunteer to step in and work 3-umpire games just for the sake of getting a routine down to the point the umpire needn't think about, but just executes.
IMO, the most difficult part of the 3-umpire system is the split-second decisions on fly ball coverage
