This is what I have for all of the verses, and the chorus of Ain't That Wrong.

Verse: Gm and C9

Gm= 3-5-5-3-3-3
C9= x-3-2-3-x-3

Chorus:

Bb major: 6-8-8-7-6-6

Eb Major: x-8-10-10-10-10

C Major: 8-10-10-9-8-8

G Major: x-10-12-12-12-12

Brian looks to be playing the Eb and G major in minor actually, but I tried it out and the Major sounded more correct. Let me know if you have more knowledge on what the chords are! Solo in G minor pentatonic blues over the verse sounds good as well