As far as muting the strings goes, the best way to do it while sweeping an arpeggio is with a combination of the palm heel of your picking hand AND the side of the thumb holding the plectrum. There is a useful pic of this on the Ziras website, check it out: http://www.theodoreziras.com/
I used to have the same problems all of the time with noise, this does not always have to do with your technique, you may be using too much distortion, also try using the neck humbuckers. I have a fair few sweep patterns in a demo track of mine at:
http://mp3unsigned.com/Showmp3.asp?mp3id=9603&aid=4890
They are far from perfect but I used the technique above with the thumb and palm muting.
Stick with it