cut its head off, there is no suffering, there is missing (we used to knock our hogs in the heads with a sledge hammer before killing them, and almost always missed, because of them moving around)(besides, would you like to be hit in the head several times before being killed?)
if you cut its head off, it will be dead before it even realizes it's in any sort of pain.
put it in a cone, though, to prevent it from hurting itself. we use old road cones with the end cut off a bit so the hole is larger. well, i should say, we normally would but my uncle has ours. i hate when someone borrows something, doesn't bring it back, and then can't be reached when you need it.
anyway, we did the last batch without cones, and a couple had dislodged wing joints. my dad held the feet, i held the head, he cut and then tossed in the grass (the tossing in the grass is optional, but you will get bloody if they are not restrained in a cone or sac, as they will jump around whilst bleeding.
also, just cut the head totally off. don't slit the throat. cut the head off, you are sure to get the artery the first shot, and the animal doesn't have to feel anything (no brain connected to the body, instant death, as opposed to brain still connected to body while blood drains).
gas it, and you're going to be eating the gas (the gas will go everywhere the blood goes, including into the meat).
shock it, try knocking it out, and you'll just make the bird suffer before you actually kill it. i would rather die without knowing i was dying, than to be beat up first