Do you have a footswitch? I find that using the pitchflex to do this works better than the other presets although you have to hold down the flex as you use it. You also get the added bonus of using it to bend to the notes. No need to select the key and all that stuff. Haven't fully tested what you are doing but I am a little impatient with the results of using the diatonic mode and most of the others really. It seems to be better with the Pitchflex on full mix, put one on unison and one on whatever you want for the harmony. The sound is better to me than trying to mix the regular sound with the eventide sound, especially for flexing. I reamped a track into four tracks this way too, it's just fast and painless once you get it dialed up right.
(switch is NOT as expression pedal, using Aux switch with FS3X)
Mix: Wet 100, Pitch Mix A+0 B+100, Ah OFF, Bh Unison, Th 0.02s
FLT:0, Snap 0, AT: Unison, BT P5 (what I use but try d3 or something I would guess).
Hold down the flex or trip it on and off for some cool wammy effect you might like it.