One of the keys to great lead playing is great rhythm understanding.
In that video...any one of those guys could play the rhythm chords to that Benson song...and because they knew the rhythm, they knew what scales and notes to play over the chords, changes and all.
So, you want to learn how to play great leads?
Go learn how to play great rhythm guitar. Learn scales, progressions, chords, inversions, substitutions, etc...