How the spell works.
1. A ring of randomly oriented bullets spawn on Luna when the spell starts.
2. A sound effect (the swooOOsh) plays, and then, as the sound ends, the spawning point/ring will start moving to your position on the screen.
3. "2." will repeat every 3-4 seconds or so, until the end of the spell.
As you hear the sound, you have about 1 second to position yourself in order to manipulate the position of the ring. I think it takes the same amount of time to move to your position regardless of distance. Luna will move around randomly during the spell, so having a few different routes rehearsed will be a good idea.
The general idea, built on what Chum said in his stream, and on what CLR does in his WR run, is as follows:
1. Move out to either side of Luna as the first sound plays, shoot her a bit to regain some ice power, then freeze as the ring comes over.
2. Quickly graze the inside of the ring like CLR does, and freeze once more with a low ice power charge,
3. Move out of the ring during the freeze and graze the outside of the ring.

*graze graze*
4. The sound should be playing about now so, depending on where Luna has moves by now, either move straight up, or horizontally across to the other side of the screen.
5. Dodge like crazy and, depending on you ice power and position, nudge Luna with your shot to regain some more power, just be careful if you move up, so that you don't accidentally move to her too quickly and end up making the ring run into her (the ice will damage her a lot!).

6. Freeze as you get get scared.
7. If you time it right you'll get somewhat good freezes, the ones from having the ring go up/down seem to give more than the ones going horizontally across.

8. Then you basically repeat from step 2, but if you are at the top of the screen you should probably always move down and not across the screen and into Luna!
Please share any ideas on improvements, or after superplay reports related to this strategy in this thread.