PlayerIndex 0 is really best for single player and splitscreen multiplayer where you have all the users on one computer and know whos who.
But basically if you are trying to do a network setup you need to cast to the Controller and HUD owner so that they are each separate.
heres a simple example for getting health from the player
note this was being made into a function just to tidy up the event graph and make moving nodes around easier.
My work flow is once I have a large set of node working or I keep using a certain setup over and over is to make it into a function which is easier to move around 