Of the various exercises you can do for speed and sweeping.
If you want to do a scale really really really fast learn to play it sweeped with legato style. Pretty much sweep the strings but hammer on or pull off every note in whatever you position you are in on the scale string to string. I hope that made sense.
Otherwise, alternate pick everything, do varied scale exercises, use a metrinome and start slowly and build with accurcy and muscles to gain speed and clarity. if you want to end up sounding truely good, work up to it, but always be willing to push yourself in exercises. Like working out, get a routine going practice for at least a half hour a day with straight exercises focus on what you want to be able to do, and go from there.
AS a shredder I can say it worked for me, and it is the most common approach to getting up there in terms of skill and speed.