ok when i sweep I dont mute with my palm but I do release the pressure of each finger slightly after I played the dont so it doesnt ring out.

As for picking of hammer-on/pull-off's I tend to hammer-on/pull-off for short 3-string sweeps to get them short and sound like there are played in one sweep; but fot the 6/5/4 string sweeps, I upstroke the second note on the high E, downstroke the third then upstroke the rest.
i.e.

------------12dwn-19up-12dwn-----------
------13dwn------------------13up------
14dwn-----------------------------14up-
---------------------------------------
---------------------------------------
---------------------------------------

hope that helps
Adam