I use one with Timefactor….I almost always set it to control wet/dry mix. Sometimes I'll use it to control feedback for A and B (set it for lots of repeats on toe down), and rarely I'll use it for A/B blend. 

 Wet/Dry via expression is awesome though…I like to get cool sounds happening, punch the Hold/repeat button, and use the expression pedal to fade my mini loops in and out.

Cheers

Kris