had a go at this today. Had to "dispatch" 10 weener mice. Felt like i was going to hell doing it, but had to be done. Part and parcel of snake keeping after all!
flicking on the back of the head didnt work at all.
I tried two other methods that worked. Put a rod behind their head and pulled on the tail worked very well sometimes, but on others the tails came off. They were dead by this point, but its not ideal as the tail goes to waste.
Another method i ended up accidently trying by badly attempting the above was simply to crush their heads. The skull at that age is very weak. However after doing this the bodies would squirm a lot for some period. Didnt seem to kill them as quick as the above method which i was suprised at. You would think having ur brain smashed in you would be flat dead!Anyhow dont think i will be doing that again. Didnt seem entirely humaine.
So i think the method of snapping the spine by pulling on the head and tail works, but is more suited to older mice with stronger tails.