I've tried a lot of methods...

At first I just threw them in a baggie and in the freezer. Then I learned that was very painful so I tried finding better ways to euthanize.

I then tried the "whacking" method. Worked very well for me at first. I just had them by the tail, found a tile floor, and threw them head first. They were gone pretty instantly. Only thing is when I did this I only had to do it once in a blue moon. The rats got bloody noses and it just wasn't pretty when I had more then a few to do..

So, I made a C02 Chamber. Liked it.. at first. The rats looked to be suffering and they took a few minutes to die. It was probably me not doing it right but still.

Then I finally tried the dislocation method. I had 16 rats to euthenize so I decided to try this. I put a screwdriver on the neck and pulled on the tail.. They were gone instantly. No pain, nothing. And it was fast. I had all 16 done within a few minutes.

So my conclusion? Dislocation is definitely IMO the easiest, fastest, and most humane way to euthenize feeder rodents. You just have to have the guts to do so.