For
Kogasa's last spell (stealing a Baity vid here because I didn't do it right in the vid I linked above for noncard 2), I see it as a repeating cycle of a few steps.
For the red arrow bullets, you shouldn't really have to dodge them at all, since it's aimed. The first step as I see it is to misdirect the two waves of red bullets slightly to the right. Not too far, as going too far to the right will mean that the next set of red bullets to the left will be fired down the center of the screen. If you get something like
this, you went too far to the right (and you're probably too close to the train besides that).
After misdirecting the two sets of arrows, find a hole through the blue horizontal amulets and work your way to the left. As this happens, the left train should have mostly passed by, leaving minimal cyan amulets to dodge.
Once you've made it to the left, it should be about time for another pair of aimed arrow waves. These should be similarly directed to the left, and you'll then work your way back to the right.
Repeat. If you follow the timing of misdirecting red bullets to the right and left alternatively, everything else should more or less fall into place. You'll still have to dodge a few scattered cyan amulets, but if you're getting completely overwhelmed by a cyan wave, your timing fell out of place somewhere.
As for Sinking Vortex, I can't say my strategy is anything more than read, read, read. Unless there's something about Murasa's movement I don't understand (as far as I'm concerned, it's random), I don't entirely count on the card going my way. Being aggressive can be a good thing, as staying under her as much as possible will obviously end the card faster, as well as reducing the variety of angles that bullets can strike from since everything will be raining from an angle relatively above you, but when she decides to be mean and run away, it can be better to just sit and accept the angle change, since chasing her can just as easily get you killed in a reckless dash.
I will add that I have a preference to dodge it from the vertical center of the screen, though I'm not entirely sure why. As I think about it, it seems like a bad idea, as being higher up increases the angles that she can attack with. I don't know. Maybe something to try if you're curious.