Try thinking of it as "Articulated Strumming." Say you're playing a G chord (example 1A), right? Go up slowly, but in one motion, and as you hit each string remove your finger, or mute the string right afterwards, in a motion like Example 1B.
Try including sweeps into your rhythm work as well, as I use them more for that than I do with leads (I know, I need to work on that...) Once you get the hang of Example 1B, try Example 2.
And finally, an example of a sweep I can play in a lead, try Example 3 once you've mastered Example 2
Example 1A:
---3-------------
---3-------------
---0-------------
---0-------------
---x-------------
---3-------------
Example 1B (sweep picked):
--3--------------
----3------------
------0----------
--------0--------
----------x------
----------3------
..^.^.^.^.^
Example 2:
---------------------------------------------
---------------------------------------------
---------------------------------------------
----------------------5---4---3--------------
-2-2-2--5/2\5--2-3----6---5---4-------------
-0-0-0--3/4\3--0-1-0---7---6---5------------
.*.*.*...................*.^^^^^^^^^
Example 3:
-------------8---------------11-13---------
--------------8------------11------15------
------97-------9-9-7/10-12-----------------
---10---------------------------------------
--------------------------------------------
--------------------------------------------
..........p......^^^...........v.v.v........ah
Legend:
*=palm mute
p=pull-off
h=hammer-on
/=slide up to
\=slide down to
^=sweep pick up
v=sweep pick down
ah=artificial "pinch" harmonic
.=just there to space things out right
Hope his helps!