Hey there, i've been catching up on Josh Urban's Crusade series on this site and lesson 9 focuses alot on the effects of pulling between chords in order to describe just why blues can get away with having two or three dominant chords in a progression when of course you can only have one (it's about secondary dominant chords basically)

But the actual features of how pulling works is escaping me, is it just the differences between the notes of the 5th of the dominant chord and whether or not they're 1 semitone apart and how they can resolve the unsettled note?