Culling chicks

I'm going on a course to learn the broomstick method for culling chickens - dreading it but need to know how to do it in case one of my hens needs my 'help' to die - hopefully peacefully.
However I am also getting some day old chicks and have been searching for humane ways for culling should the need ever arise. The American vet association recommends the use of carbon dioxide (formed by mixing vinegar with baking soda) http://www.alysion.org/euthanasia/
Has anyone here any experience of this method or any comments about it?
Horrible subject, sorry.
Jane

It's really about needing to cull in the event of deformity or illness.
Jane

If I had to cull chicks, the brooder they were in had a hardboard circle which kept the warmth from the lamps in.

It is very easy in young chicks to just hold them gently, put their neck on the top of the hardboard cand quickly press down.  You will feel the vertebrae snap.  horrid job, but very quick and humane.

Any other sharp angled item is fine, shelf edge etc.