Watch the Magic V online guitar lesson by Jeff McErlain from Solo Factory: Chicago Blues
This is one of my favorite licks to play on a V IV I turnaround in the blues. It's a classic, and something you hear magic Sam play on his version of Sweet Home Chicago. Licks like this take some time to get into your playing as it works specifically on the turnaround, in other words if you miss work start it won't work! The way I recommend practicing something like this is to use the track enclosed, play it until you're blue in the face! Try it in different keys, tempos, and feels. Overuse it! This way it becomes part of your vocabulary and you will know exactly when to use it and you'll have it under your fingers.