Chicken Slaughter and Butchering Process: Flow Chart
I have not butchered a chicken in 8 years, but because I did my homework and documentation then, I expect no problem with 20 birds now. Improving a process starts with documenting the process as-is.
See also the video series of four, which starts with:
My buddy had a sleepover I attended, and in the morning his dad demanded we help him slaughter chickens. Not what I signed up for, but it was awesome.