There's a couple of different ways to get that wah "filter" sweep tone all the time...

1. Do NOT roll off the mids... you lose definition and sound like a BAD AM radio...
2. Put a distortion pedal into the mix (DS1, etc.) with the tone turned up totally treble
3. If you really want to get a thin sound, change one of the pots on your guitar to be a push-pull pot and have it wired to go out of phase.

So, there are a couple of options outside of what has already been mentioned about using an EQ, etc.

Hope this sheds some light :-)