I use a VooDoo Labs Ground Control Pro and GCX switching with my factor pedals. It saves presets so I can instantly jump from say 4:2 to 35:1 with the push of one button. I can also assign the same expression pedal to multiple Factor (and other) pedals. Depening on the preset, My expression pedal will controll the Pitchfactor on one preset and the timefactor on another preset. The GCP can operate with two expression pedals for greater flexibility. All the features (bank up/down, bypass, tap tempo, etc.) are available for controll through midi so you can do it all with the GCP.