Watch the Sustained Phrases online guitar lesson by Robbie Calvo from Power Phrasing
Playing long sustained phrases that just hang in the mix are also a very important way of expressing yourself over a cool blues/rock track, or any style of music for that matter. The example you heard me play was a series of double stop ideas and single note parts that really sat on the chords and created ambience and space. These types of phrases let the listener interpret the music. It takes them somewhere and they can start imagining visual images that you conjure up through your sonic palette of tones.
Creating a sound that sustains nicely and hangs on the air with the use of mild overdrive, reverb and delay is a good place to start. Then you need to use your taste and expertise to make every note count. The double stops work really well because they add a harmony part to these simple lines. Major and minor 6ths, fifths and fourths combined, are nice too. Experiment with your choices until you find some nice parts to work with.