Any CC number from 0 to 99 can be used for MIDI control. A Continuous Controller message has two parts, though: a controller number, followed by a controller value. If you're using a continuously variable controller – such as a knob, wheel, or expression pedal – you might have CC1 (modulation) as the controller number, and the pedal will send a value somewhere between 0 and 127. The value depends on the current position of the expression pedal.
Switches are going to be a little different. You can still pick any CC number, but a switch will only have two states: On, or Off. The 'Factor pedals will consider any controller value between 0-63 as "Off", and any value between 64 and 127 as "On". It's going to depend on your MIDI pedal whether it just sends an "On" value, alternates between "On" and "Off" with each press of the switch, or perhaps sends "On" when it's depressed, and "Off" when it's released.
As I said earlier, I'm at a disadvantage on exactly how the MFC10 works. But it can't hurt to try. In the same system area where you programmed your expression pedal – MIDI: RCV CTL – look for the FS1 / FS2 / FS3 entrries as destinations. These will give you the footswitch functions opposite of the 'Factor pedal mode that you're in [Bank mode functions in Play mode; Play mode functions in Bank mode].
Of course, the AUX SW system area can give you many more options than the 'normal' pedal switch functions. Same thing in the MIDI system area. If you want a specific function tied to the MIDI switch [Bank Up, Bank Down, Tap, etc.], just rotate the encoder knob to customize your setup.
As detailed above, if you already know the CC#, enter it next to (for example) FS1 > cc# entry. Or tap the right footswitch again in this system section to get to the LEARN area, and tap your MIDI footswitch for the 'Factor pedal to recognize it. If LEARN doesn't work, you may have to go back and check your MIDI channels, OUTPUT setting, or the MFC10 transmission setup (both the continuous controller number and value).
If you have your expression pedal working, then your MIDI routing is already where it should be. Just treat your MFC10 switches as if they're expression pedals with only a "heel" and a "toe" position. There are other adjustments you can make (range limits for KB0-KB9), but that can wait. Let me know how it works out for you.
