putting down

Hello, I come back for a simple question, we have a hen who's not doing well and we are now thinking about trying to put her down just so she stops suffering. We have never really put down our birds except for once and that was our first year of getting chickens so we don't know how to put them...

So, I'm feeling "stuck." I'm not certain of what caused her wry neck issue but, in my effort to rescue/fix/heal the situation I ended up with an aspiration complication. (Heavy sigh) I need to ask what is the best/quickest/clean method of putting her down. I am not looking forward to this...