Bobby Pfeiffer recommends Visual Guide Tones:
"Through the study of visual guide tones I now can see the Pentatonic scale all over the fretboard in every key, the Major scale all over the fretboard in every key. a scale Dana calls "Dominant pentatonic" all over the fretboard in every key, and the Melodic minor scale all over the fretboard in every key. This is huge for me!!! and has totally changed the way I play and what I can play over!! These scales cover almost all the chord types in music and I am able to improvise over chord progressions and tunes that I had previously given up on, using MY STYLE, I am no longer relying on other people's licks or having to memorize phrases or pre determined formulas to get through changes.
If you want to eliminate the gray areas on your fretboard and improve your technique.... get VGT!!!