The amazing part about this film is not the actual movie but the person it is portraying. As the director stated, the documentary can hardly do justice to the man himself. He is an absolutely "no-nonsense" guy with that remarkable Zen-attitude everybody would love to have. And he worked hard for it. That strong personality easily transcends the rather conventionally structured documentary. Sometimes back-story is impressive but in this case it doesn't add or take from the impression, which is a notable thing.
Should look for actors with that kind of quality.