The killing cone seems to be the best method I know of. When placing the chicken/roo in the cone head down and waiting a few minutes they go semi unconscious. Once they have reached this stage you simply use a very sharp knife to cut the blood vessels in the neck. They bleed out quickly without all the fuss from other methods. Once they are sort of unconscious I don't think they feel a thing. If you are doing several chickens then more than one cone works even better. They get more time to settle down and you don't have the stress and fuss.
