I've never seen a skunk not spray with a head shot, they always do. I've had better luck shooting them in the lungs.
Same here, been trapping about 47 years and I'm almost certain every one shot in the head released, it's not an out and out spray but always a release as it kicks. "Sometimes" a lung shot will not release. I still shoot them but a relatively sure way to avoid it is a jabstick filled with acetone in the lungs.
For a non-messy live catch put the box trap behind your exhaust and cover the trap and exhaust with a tarp, let it sit a few minutes.
