8 Bar Blues - Key to the Highway (Little Walter)

You probably already know that 12 Bar Blues is the most common form in blues. What's the second most common?... 8 Bar Blues. Listen to Little Walter's version of "Key to the Highway." Knowing that 2 Draw is the root note of the I Chord (one chord), 1+ is the root note of the IV Chord and 1 Draw is root note of the V Chord, see if you can figure out the chord progression. You'll need your C Harmonica for this (the song is in the key of G).

Hint, the first four bars is a standard V-IV-I-Turnaround, then it goes into an 8 Bar Progression.