Here is something I just learned today, while playing preacher chords.
Each blues scale can be played in five keys. Let's take the C blues scale.
C, Eb, F, Gb, G, Bb, C
You can play this same scale in Eb, F, G, and Bb.
Eb, F, Gb, G, Bb, C, Eb
F, Gb, G, Bb, C, Eb, F
G, Bb, C, Eb, F, Gb, G
Bb, C, Eb, F, Gb, G, Bb
When I tried starting on G and Bb, it didn't stick too well. Although it worked better in G than Bb, it sounded better when I used it as a transition to C or Eb. Maybe you can get it to work.
It doesn't seem to work in Gb at all. So to sum it up, if a minister is preaching in C, Eb, F, G or Bb; you can use this same scale.
