The first 12 bars of what Guitar Slim plays over "The Things That I Used To Do" is a great example of 2 powerful concepts: First - using both the triplet, slow blues, feel along with the occasional set of straight sixteenth notes. BB King is another player that uses this a lot and it always sounds grreat. Second - he uses what seems to be the major pentatonic sound over the IV and V, but notice how he very carefully avoids the one note that would make it sound bad. Website - https://BluesGuitarU