This rhythm guitar part is a 12-bar blues in the key of G.  There is no quick-change to the IV chord (C) in bar 2.  The turnaround at the end of the first chorus is a simple I-V type.

The chord licks are all derived from the same basic triad shape for each chord.  You simply move it up or down the neck for the I, IV or V chord.  The chord shapes are used are given in the score, though once you see how it works, they really aren't necessary.

This is a fairly active rhythm part, but because it is repetitive, and hopefully, not too loud, it doesn't overwhelm the soloist or singer you would be backing. The rhythm as well as melodic (lead) use of chord shapes is covered extensively in More Blues You Can Use, the second book in the BYCU series.

In lessons 1 and 2 of the book, the melodic use of the triads used in this lesson, along with seventh chords, are explored in a 12-bar blues form.

In a completely different style, lesson 10's rockin' "Eight-Bar Boogie", offers another way to use these triads in the rhythm as well as in the lead part.  Listen closely for the rhythm part in the right channel - I've boosted it for this example.

Listen to the audio sample MBYCU Triads located on this page for an example of how they sound. This is a laid back tune with a down home feel.  When you play it, just relax into the easy groove.