The only 4-5 trill in La Campanella it's not really a trill, it's just three beats like 4-5-4, any other spots I worked around 45 trills...For 4/5 trills I personally twist my wrist outwards, well not twist, but when my pinky plays the note, it's the closest part of my hand to the piano, so the rest of my hand is diagonal upwards from it...I lift the thumbside up, and I find it makes it much easier to play those trills, personal preference, I just find it easier to do that...