The first thing you should learn about sweeping is the picking motion , you should get it right at different tempos , and know when and how to change from down to upstrokes and vice versa .
The second is to concentrate on how to fret a given pattern with the correct fingers (this is very important , if you don't choose the right fingers , you'll have problems when playing faster) .
Then comes the muting , all you have to do is practice what you learned over and over with distortion ,and try to make it as clean as possible.
If you're having troubles with a specific line post it here, so I can give you more detailed help ... BTW, you should have posted that topic in the "technique" section ;) .