Watch the Rhumba Blues - Part 2 online guitar lesson by Jeff Scheetz from Blues Jam Survival Guide
There are several variations or approaches that we can use here. Not only doing our main riff, but using chords all in one position to minimize the movement. This is essential for players who are singing, because it keeps them from having to move too much. Also there is the option to pick through a chord which works really well if you are playing with another guitarist who is comping on the chords.