When im sweep picking I sometimes double pick the note when im changing directions;meaning if I go from 8 to 11 on the E string, instead of hammering-on I will double pick the 11th so first pick direction would be an upstroke then down stroke that would get me ready for the up-stroke for coming back up the strings ex:

E ----------------^8---V11^---V8----------
B ------------^9-------------------V9-------
G -------^10--------------------------v10----

If you watch sweep-picking carefuly you will see this being done, its a very small movement but its a common sweep picking technique :cool: