After watching that Paul Gilbert solo and some of the other shredders, the one technique thing that I find common between them is that they aren't moving their index finger much especially on those fast runs. What I mean is that the index is almost the anchor point for those scales and only moves up or down a string. Obviously it moves to different positions on the neck, but everything kind of revolves around that index finger as a pivot. I've never been that fast, so I've always kind of looked for the secret to these guys technique that allows them to play through those scales so quickly.