I know it is ridiculed but I use my air rifle.
It might be over the top, but I know they are dead in an instant.
One pellet behind the ear aimed towards the beak has never let me down yet.
Until I have someone here to show me, in the flesh as it were how to do it otherwise, I'll stick with this method.
I have tried dislocating the neck of a freshly dead rooster and I can't do it

I KNOW it must be my technique but that is no comfort to a live bird should I wish to practice that method