I climb with that same system all the time, but use a petzl hand ascender. I also put the pulley on the top hole with a non-locking carabiner(prevents the rope from accendently slipping out) I can remove the pulley and carabiner in a smooth fluided motion, and move it to the bottom hole on the ascender, then remove ascender and clip it on my belt in only a few seconds to work off the gri gri or decend.
I rarely use the foot loop except for really long ascends, for less then 40 ft. I hold one hand on the ascender, the other on the rope coming off the pulley and footlock, so i am pulling with one hand as I push with my feet. Even if you can't footlock, you can footlock like that, it effortless. That way your not a slave to that footloop that's always getting lost.
Today I used that same system with a rope wrench and my regular set up, a Vt and three holed pulley, instead of the gri gri. It almost worked. my prussic was to long so each time I pulled my self up a foot, it would come back down 8 in. before tightening. Couldn't make much headway. Maybe a shorter prussic would work with shorter legs?
Also I don't ever use that sling that connects the hand acender to the gri gri. I don't see why its needed.