The pithing waterfowlers do is done from behind. You grab the head and bill and bend the neck with the bill 180° pointed to the chest and insert the pith where the spine meets the head into the brain and they are dead.
That said, I windmill mine and snap the neck. Chickens squirm a lot more dead than other fowl. The times I have loped heads they normally threw blood all over me unless in a cone. I have not tried the pithing to see if it quits this, but I doubt it as separating the head from the neck doesn't.