If you do a google search for "killing cone flashing" you'll find several ways to make metal killing cones out of roof flashing. Basically you get 16" roof flashing and cut a length of about 30-34 inches. The you measure to the center and mark the midway point. Then from this midway point, you measure out about 8-8.5 inches and mark those points on one edge of the flashing. This will allow you to cut the flashing so it's 34 inches long on one edge and 16-17 inches on the other.
Then you mark a line from one edge of the flashing to the other, starting at one of the end corners and going diagonally towards the nearest mark you made from the centerline. Then repeat with the other end. Use tin snips to cut the line. Then you roll the flashing up and over lap the ends by about an inch. Drill 3 or 4 holes in the overlapping part and secure with rivets or bolts. If you use bolts, put the bolt into the holes from the inside and the nuts on the outside so there is less for the bird to rub against. Carriage bolts would be good for this because they are rounded and smooth.
Since this is a CSA, catch the blood in a bucket and compost it, or you can do what we do. We have wooden compost bins and we made a framework so that there is a horizontal wooden beam that is over our bin. We use this to hang the chickens from while bleeding out and the blood goes right into the compost so you cut out the middle man (bucket) so to speak.
I think you're definitely right about bleeding them out. Since this is a community operation and you'll want people to be able to store their birds for a while in the freezer. Getting as much blood out as you can will increase the storage time. You need the birds heart beating to get that blood out. I think it also makes it taste better to get the blood out.
Don't know if you have a plucker or not. There are some great threads on homemade pluckers here. you can make cheap ones that are drill mounted (don't use a cordless drill, make sure it plugs in). Or you can make a "wizbang" plucker that will completely pluck a whole chicken in about 30 seconds without you having to touch the bird. You just drop it in the plucker and let it go. If you have lots of birds to process, which I suspect you might, a wizbang plucker is the way to save yourself lots of time. You still might have a few pins to remove but that's easily taken care of with a pinning knife or table knife. Needle nose pliers work too if there aren't too many however I spend more time cleaning the pins off the pliers than I do pulling pins so a table knife would work well because you just wife it to get rid of the pins.
I'd set up stations. You have your killing cones, your plucking, you're gutting, and your cooling/storage. Have the people do several chickens at each station and then rotate.
For the storage/cooling, have a couple of clean 33 gallon trash cans or those big 55 gallon plastic barrels with a top cut off. Get LOTS of ice and you can use those to soak/ice the birds until they are ready for freezing. Salt will help to lower the temp of the ice, cooling the birds faster. Let them age for 2 days or so and then part out (if you want parts) and freeze.
Dan