Well, as one who dispatches dozens of rats every week, I might be able to help. As you may know I raise my own feeders so everything I feed is F/K with me doing the "K" part. For the larger rodante smacking on cement is surely an option but can get a bit messy. There is a fine line between hard enough to kill and so hard you cause hemoraging....bleeding out the nose. What I do with mine is to whack the spinal column right behind the head. Incapacitates them in a hurry. Simply swing by tail and aim to hit back of neck on hard sharp object, I aim for the edge of the bucket I transport them in. Properly placed blow and they just twitch for a minute with no bleeding whatsoever.
Yes it's gory
yes it's gruesome
yes it's a necessary evil
no, it's not fun
Like already said only other option is CO2 chamber but there is expense there. And I find for myself since I don't freeze, whacking one by one allows me to feed my snakes one by one and not waste any, if one does not eat, I give it to another.
-----
Thanks,
Dave Colling

www.rainbows-r-us-reptiles.com
0.1 Wife (WC and still very fiesty)
0.2 kids (CBB, a big part of our selective breeding program)
LOL, to many snakes to list, last count:
24.36 BRB
19.19 BCI
And those are only the breeders 
lots.lots.lots feeder mice and rats 

