The John Petrucci Guitar Method - Episode 6: Scales on 1 String, 2 Strings, Playing in 3 Octaves
For tabs: https://www.guitarworld.com/lessons/the-john-petrucci-guitar-method
In episode 6 of "The John Petrucci Guitar Method" John discusses playing scales on one string, on two strings, and how to play in 3 octaves.