Back on the tip dry thing (I know, debating milk is so much more fun, but bear with me.)
Basically, every paint ever made by any company has, at one point, advertised "zero tip dry!!!!", and they've been full of it.
.
When you're using an acrylic paint, which dries faster with air movement, through a device that directs compressed air, you are going to have tip dry. Some paints are better than others in that regard, but it's just a fact of life with airbrushing.
The good news is that you will eventually get so used to it, it, too, becomes second nature to clear your airbrush and pick the tip. Eventually, you just know when it's building up on instinct (which I still swear I can hear the sound change when tip dry is building up).
Polishing the needle definitely helps cut down on tip dry, I've found. A search on here will probably give far more information on polishing needles than you'd ever need. It also helps with the airbrush performance, so, IMO, it's worth the time.
Additives like E'Tac condition-air or glycerin can help tip-dry, but they also slow the dry and cure time of the paint. If you use too much, you can wait a very, very long time for it to cure (yes, I know from experience. a few times.). But, used in small amounts, they can save a lot of headaches.
Also, the wide range of reduction amounts you've seen recommended show that there simply isn't a "right" answer, other than what works best for you (which can change over time, too). It comes down to trying it out, and playing around with it. See how thick you can have it and still spray well. See how thin you can get it and still control it. Basically, just experiment with it, and find how it works best for you.