All of the pitch flex presets are designed to work well with an expression pedal. So, what you're going to want to do is assign a MIDI CC to control the expression pedal patch. There may be one assigned already by default. If I had a PitchFactor with me I'd check, but I don't. But if you go into the system settings of your PitchFactor, you should see that in the MIDI settings section.
