I remember this processing as one of the most fun tricks I did with my EDP. WHat I did was to set feedback down to zero, make a long loop, put in Overdub mode and play. When pressing Reverse the stuff I just played into the EDP came back reversed while the new stuff I was playing (on top of that) was overdubbed (to be played back reversed after hitting Reverse next time).
Michael, what software looper were you able to pull off this trick in? SooperLooper? I think it works with Augustus Loop too. But not in Mobius - unfortunately. Mobius needs to fulfil the full loop length playback before printing the currently captured overdubs as a new loop layer - and when playing this "freestyle reverse-ing" you may often hit reverse before reaching the loop's end point.