Shine stalling is incredibly good if it is done correctly, and when mixed with shortens and good up-b angles, it makes for a tricky edgeguard. You can practice angles just on your own but applying them in matches can take some time and experience. The thing that helps with recovery is thinking, "What would I cover, if I'm edgeguarding?" because then you have a better guess at what your opponent is thinking and trying to cover.
Shine stalling is mainly useful because it throws off the timing of your recovery and in a way turns your recovery into reacting to your opponent. For example, Sheik has you off stage they may try to read an illusion with run off DJ Nair, had you shine stalled you can react to the Nair and recover accordingly. When close to the edge shine stalls can also be used to find a place to safely sweetspot the edge. Obviously mindless shine stalling will get you killed so it is important to mix up whether you shine stall or not.
As said before, learn ledge dashing, doing it well forces your opponent to respect the option because of your invincibility frames.