Watch the Walkin Man Blues 10 online guitar lesson by Carl Verheyen from S.W.A.T. Blues
The concepts in this lesson apply to what I like to call "level 2 and 3" blues playing. This is when you're ready to break out of level 1, which is minor pentatonic on the entire progression, and graduate to level 2, which is minor and major, and level 3 which incorporates the mixolydian mode, too. There is also the swampy double stop concept demonstrated as a tool to go beyond the single line approach like we demonstrated in the Diamond Blues lesson using chords. If you're stuck in that blues rut, I hope it helps you break out of it!