Watch the Outside Sound: Over A Blues online guitar lesson by Rob Garland from The Guitarist's Pentathlon
I'm using the outside sound on the turnaround of the A7 blues, moving two notes from the Am pentatonic scale up by a half step. I also suggest experimenting with this as the I chord moves to the IV chord as I demonstrate moving in and out of the pentatonic scale. Try simple rhythmic ideas, be patient and be confident. That way the blues purists won't come to get you in the night.