The ones I've bought usually already had some sort of sealant on it.
The last time I needed one was a few years ago and every one I tried had the problem with the wing that spun before it was tight. I ended up buying a compressor drain valve that looked the same but made better for about the same price. No problems since.
on both
Yes sealant. Loctite blue works excellent and you can wipe off the excess.
On the drains, Exactly what I did, bought 10 or them, made by Milton in this country
But they don't have the little extension om the end for a hose, BUMMER!
The parts store ones cost me about 3 hours or more of utter frustration
