Watch the Someday Baby Solo online guitar lesson by Jeff McErlain from Essentials: Advanced Blues Soloing
The big payoff on the solo is the diminished seventh arpeggio in Bar 3. Well, there are other cool things of course, but let's discuss that one. The chord is a B diminished and is referred to as a #IV, as the IV7 chord is Bb7, raising it a half step making it a #IV chord. The notes are B-D-F-Ab, all of which are equidistant, all separated by minor 3rds (1 1/2 steps). So, interestingly, any of those notes can be the root. So, you have actually learned four diminished 7th arpeggios in one! Huzzah!
I'm starting on the root on the downbeat of Bar 3 playing 16th notes and ending on the root of the F7 chord on beat one of Bar 4. The timing on this is essential, and very cool if you nail it. You can use this link on any diminished seventh chord, or you can also superimpose it in Bar 6 on a standard 12 bar blues.