Skinning can be harder than you think with older birds. You might need to use pliers to pull the skin off if you have weak handsWho me?
I actually didn't realize how many chickens you still had given all the Marek's problems until I read your interview. Yeah you do have a lot of chickens!
I gather the only REALLY important thing about butchering is to make sure you don't cut into the digestive tract AT ALL. Some people do a rinse in chlorine water just in case. As far as plucking vs skinning, if you aren't going to roast it I've heard skinning is WAY easier and faster than scalding and ripping the feathers off. Makes sense to me.