Yes I play with a Jazz Singer also. When it comes time to do a solo I do some things that make myself cringe! First of all, I'm not the teacher here, Im very mediocre soloing in this context, but Let me share a few things with you that have helped me:
I often turn to a lot of chord soloing, trying to sound like a big band, with a lot of "rhythmizing" for lack of better word. Since I don't have my single-line vocabulary up to where it needs to be, this helps a lot. Also I just do some short three and four note motifs..... and Try to keep that going over each chord, call and response, etc. etc. I'm sure Barry Will elaborate and expand on this (if he wants to) otherwise just seeing and hearing him play we'll do the trick for me!
As far as chord stabs, I don't limit myself to just that when soloing, my thinking on this is when we are soloing, at that point we are the entire band....... We can hit any size chord, partial chord, Octave, bass line, single note........ Whatever we choose......... But again this is just my take as I mentioned my skill level in this it's poor to mediocre. We are lucky to have someone like Barry that can help us improve with all this!
Couple of quick other things: as Guitar players, we are always told to not interfere with the singer. However, On some tunes I play the melody on top of the chords and I asked the vocalist if that's okay and she said she likes it?! I wonder what Barry thinks about that.
Lastly, among other things, some practice devices I use for this, are trading 2s and 4s with myself............ And also, taking 4 and 8 measure, or even smaller sections of the song and see how many variations I can come up with........ In all different areas on the fretboard.
Anyway I have found absolutely no instructional materials available on this, aside from my own transcribing and I think it's fantastic that Barry is willing to consider getting involved with this.
Aside from Solo Guitar, This is fantastic also because we could use all these techniques when playing in a trio or a duo with a bass player also! Or really any situation!
Bob B