Cervical dislocation is hard to master but once you've got it, you've got it. Co2 is virtually painless, and you can probably make a chamber for free out of house hold ingredients, and then dry ice or vinegar and baking soda.

I don't think anyone should be complaining about how much 'work' it is, when the few minutes it takes to set up a chamber, or the few seconds it takes to CD shouldn't be more important than the welfare of the animals in question.