It would be cool if you could power the motors through pads on the delrin wheel, connecting through a spring loaded terminal (probably a technical name I couldn't find). That way you wouldn't need to worry about the wires twisting and if it became misaligned, it would just fail to do anything rather than make a mess.
"Slip rings". Sometimes expensive, but I bet the surplus houses have a bunch.
Sparkfun has audio transducers that might be a convenient way to vibrate your flour dispense funnel to get it to deliver the full load. I connected these to soup cans for a project, and they vibrate nicely esp at resonance:https://www.sparkfun.com/products/10917A pager motor might do just as well, and is probably cheaper.