MoF Stage 4 Lunatic ReplayFor the first waterfall at 24 seconds in, I mislead the aimed bullets off to the right, then dash off to the left and stream to the right (it's a bit unintuitive to go through that left waterfall, but ever since I first saw this method I've used it and it's always worked for me). As for the second waterfall after Momizi, while
it can be done, I'm going to be blunt: don't try it. Note that in the full-stage replay, I drag out the Momizi fight a bit, which is specifically for the purpose of shortening the waterfall into something I can dodge. Unfortunately, Momizi is difficult herself, so you'll likely have to bomb her, which goes against dragging her out. But for the sake of raw survival (I'm assuming you're trying to work on this stuff so you can try for a 1cc), don't hesitate to bomb either Momizi or the waterfall.
Unfortunately, Aya is mostly a straight-forward skill boss, as there's not much of a trick for most of her attacks other than being able to simply read things. The only one that has a trick is her second noncard, where if you sit directly under Aya, then move just enough to dodge the blue circles that will be fired directly at you, you should graze everything that flies by, though I'm not entirely sure of the details of how this works as I still mess it up from time to time, but I think you want to dodge as late as possible to make sure the red stuff doesn't hit you.
Also, while I don't have any samples of your playing to examine your playstyle, I'll say this just in case: don't be afraid to move up from the bottom of the screen, as hugging the bottom can prove fatal at the Lunatic level in general, but a lot of Aya's cards specifically can wall you if you do so.
I'll also add that some people employ some sort of counting system for dodging Aya's final, but I don't know anything about that and personally just play it by eye. It might be something you want to try playing with though.