The best way to learn by ear is by selecting good players on you tube and listening carefully, and replaying for fine detail, but sheet music can also be useful.
as far as i am concerned understanding what I am doing harmonically is helpful, but whatever works for different people.
People like Michael Gill who are didactic about music learnibg are narrow minded, and people i try and avoid, from the description jack campin gave of him dissing sessions online , he sounds rather negative