Some of the best sweep pickers out there: Theodore Ziras (do a search for his site on google, then check out the video clips - look at his picking hand, it does very little work, there is a trick to the technique), Michael Angelo BAttio - one the cleanest fastest biggest arpeggio sweepers around, Frank Gambale - invented some new techniques to make the patterns easier and clearer, Rusty Cooly - eye poppingly fast, Michael Romeo (from Symphony X - he has a solo album which has some of the most impressives sweep patterns ever made) and of course... JAson Becker - one of the first real serious neo-classical fusion shredders. Checkc his site outm there are a frew snippets from lessons and clinics when he was in good health. There are many more, these are just the first to jump to mind when you mention sweeping.

Check out the above guys online, you'll pick up stuff from a lot of websites about their techniques.