Neat idea, and a little insane - perfect!
I find painting 2-3 at a time hits the sweet spot for me. no burnout from painting conga lines, but much more efficient than one at a time. I also suggest painting monsters, undead, n' such. proper humans have loads of expectation bolted to them- they need to look a certain way. undead can be downright grimy, and look perfect. monsters often don't wear clothes so they can be painted easily with some very simple speed-painting. Id attack bones 4 critters pretty hard;lots of stuff there could be painted in a snap (eg Darkreach had a lot of monsters that would look great with a few colors and a dip). Shameless plug: this is exactly what the leeches were made for - they are stupid easy to paint and there are two of 'em. Knock them out in 30 mins or less!
I talk big, but there is no way I cold do this this year. Ill put a pin in it, though.