The easy way that Broonzy plays Guitar Shuffle makes it all look a bit too easy. In fact, it isn't that hard to work out what's going on, but as always with Big Bill, the swing feel and the speed at which he plays is the big challenge.
He recorded Guitar Shuffle many times, in slightly different forms, with slightly different riffs and simply re-named it to something else. The tune shows Bill's complete mastery of the guitar and is difficult to copy properly.
The trick is to play it slowly and follow the tab to the letter. Over some weeks gradually speed it up until it's moving along at speed AND you're hitting all the notes.
I'm pretty sure that Broonzy used mostly his forefinger and thumb to pick these masterpieces, but some of the runs are so fast that I think he may have used a second finger now and again. Guitar Shuffle is played in the key of C.