How much pressure does it take with your thumb? This is something I hope I don't have to do ever, but I realize I'll probably do it at least once in my life. I even felt a little bad killing some rats with co2 even though the alternative would be feeding them live to a snake (which is a much worse way to go imo). I've read about a hammer and everything but I've hit a few nails before and my aim is not something to brag about. While I'd hate to feel the squish I'd feel better knowing it was done right and done quickly with the animal feeling as little pain as possible.