The first time I had to cull a chick, I couldn't bring myself to cut its head off, and I felt terrible about freezing it to death, so I figured I could break its neck very quickly. Well, I used way more force than necessary, and the head came right off. After I got over it, I realized how quick and painless it was on the chick, and have stuck with this method. Don't get me wrong, I HATE having to do it, but if you're going to raise chicks, it needs to be done occasionally.
The point is, I think you need to do what's easiest for the chick, not for you! Good luck.