Back in 2005 I attended a clinic with him and had to opportunity to ask him who he has learned all these voicing's.
Me: ”How did you practice all these voicing’s – and how do you learn new ones?”
Kurt: “That’s a good question. I take a lot of stuff up scales. I take any voicing, and some melodies come out of that. I’ll find a certain quality of a chord and try to find voicing’s of that same sound allover the neck. And that’s by thinking about witch scale it’s from. For example E7(#11) is the scale of B melodic minor. So then I can see the scale on the neck and I’ll find voicing’s for that sound, just using notes from the scale.”E7(#11) (Update: The 2. vocing is wrong!)
This is a clear example of a jazz musician who knows his melodic minor. The way he investigates chords relative to a scale, seems like a very good way to enhance ones overview of the fretboard.