Music of the Night from Phantom of the Opera is my jam for learning to separate bass and vocals in my head. Good times!
+1, learn to play without looking at your fingers. An essential skill for singing bassists.I am able to sing and play the bass just with one song where I don´t have to look at the fretboard which is in my opinion the first step to do. I think the mere gazing at the fingers can confuse the brain.. but it depends, it´s all very individual...