The "one fret away" bit of wisdom is rightfully credited to Shawn Lane. He played so fast you would have hardly noticed if he missed a note, but credit where it's due. I'm just the messenger.
I would challenge anyone to just "belt out a solo" without understanding key signature and the scales that back it. You might be able to do that if you're playing someone else's songs, or if you're playing everything in one key, but generally speaking, you're going to miss a whole lot of notes if you don't.
On belting out a solo - It matters not whether the soloist knows it, if he/she is 'belting out a solo' and the notes work, he/she has used scales to do it. Whether through the artist's practice or intuition, it was a scale that allowed the solo's notes to flow together. So, if you haven't got the kind of intuition it takes to do it, practice scales.