I personally find it easier to practice OBE meditations by listening to binaural beats. Not only does it keep me focused, it blocks out other external noise. I have also found a nice guided meditation on awareness. They're not necessary but I like hearing new perspectives and routines sometimes. I have read that it is counter-productive to become reliant on aids like that and I can understand why. It's kinda worthless to learn how to do those things but only under very specific circumstances. And I suppose one can argue that it poses less of a mental challenge. However, I don't see the harm in switching back and forth between methods to mix it up a little. Whatever floats your boat.