Trills are weird. The more obsessed you become with them, the more difficult they are.
It's really only logical that the best approach to them is to take your two strongest fingers (wherever possible), thoroughly loosen your entire "mechanism" (wrists, arms, shoulders, back, hips) and just let fly.
With a relaxed mechanism, you can trill for days with total control.
I think so-called exercises to learn to trill are absurd. They only result in more obsession over what is a completely natural, basic and potentially simple keyboard task: the repetition of two adjacent notes.
I mean, how hard is THAT?
But, when you begin to think and think and think about it -- analyzing it to death -- you begin to grow tense. And tension is a trill-killer, for sure.
Trilling on 4/5 I wouldn't even get near unless I absolutely had to. And 3/4? Almost as dumb. These fingers, for most hands, are physiologically weak to begin with. The tendon design by nature is limiting. That's how Schumann got into trouble -- trying to make 3/4 do what they are not designed to do. To get 3/4 or 4/5 to function with control and a semblance of speed and power requires a good rotation technique. Not increased "muscularity."
Go for the strongest fingers 1/2 and 2/3 whenever you can, and just warble away.