I use the Earl's speed bleeders on a couple race cars. Next to sliced bread and butter they are the best thing to come along. There are different threads available so make sure to get the right ones. They do come with a thread sealer on them and over the years screwing in and out may wear this down enough to let air bypass when bleeding, but that time hasn't come yet.
Also there is a special wrench to fit these, looks almost like a 6 pt box end wrench but it is cut out to slip over the tube or whatever. Like a flair wrench. Suggest using one of these. And when you close it, work it back and forth to seat the inner flange, shouldn't take much really to close it. Don't give it one big turn when you close it. Burnish it in.