Yes, it sounds a bit too 'fiddly' to be practical to me too. I know the 'roller blind' idea as mooted by cvdc works, but I would suggest the use of weights on the chords that can hook onto the side bars of the rig, As you unhook the weight it drops/lifts the next backcloth, allowing a very quick changeover. With practice you can unhook them with your elbow, still keeping both hands free!!
Weaselly distinguished, Stoatelly different!!