Watch the Grease-E online guitar lesson by TrueFire from Play Blues Guitar 7: Slide Approaches
Grease-E - Lick 13 is a video guitar lesson presented by Andy Aledort and is sourced from 30 Beginner Slide Blues Guitar Licks You MUST Know.
Let's stick with this thematic approach for the moment; it's a great way to build a repertoire of licks while also focusing on a few very specific technical aspects of slide execution. One of the beauties of the open E tuning is that a fifth and flatted seventh can be sounded simultaneously by laying the slide across two strings at the same fret. Over E, this would be the second and third strings at the third fret (or 12 frets higher at the 15th fret). Sounding the fifth and flatted seventh together is a cornerstone of slide soloing and has been used by virtually every slide guitarist ever.
In this lick, I begin with the phrase, sounded by alternately picking the second and third strings while the slide is positioned at the third fret, after which I slide down the neck and move to progressively lower strings.