EkoPrime for me
I've used EkoPoxy, EkoPrime, Rustoleum Pro (not self etch - so manual scuff), Duracolor and Rustoleum self, etc. For me, EkoPrime was the winner by a landslide. Super easy to spray, and no waste since it doesn't get mixed with a catalyst. It's plenty durable , and like most primers gets tougher the longer it sets. The bonus is that it doesn't stink up the place forever while it dries. The rattle cans are fine when I just have to hit some small parts, but I've found it all to be very soft initially and not very durable even after weeks of curing (at least relative to Stewart).
I've primed virtually everything in the plane so far. That being said, for the next plane, my strategy will change to only priming mating surfaces and parts that aren't alclad. With that approach, I'll probably switch to something like SEM for the convenience factor. If I were in central Oregon and that's where my plane slept most of the time, I'd 100% go with the minimal priming approach for mating surfaces only.