I find it hard to give verbal tips for something like this, so.... instead, here's a video showing the technique I use.https://www.youtube.com/watch?v=C1Z-PWTsJe0
I do have a couple of derp moments in the third phase, but that's what happens when I get impatient.
Obviously though the technique for the first two phases is a sort of slow up and down movement, so as to get away from each "cloud" of bullet spawners as they appear.
In the third phase, well... it's all about reacting. And sometimes getting BEHIND the arcs when you can. Take your time and use missiles if you need to. This pattern is one of those that's designed to make you panic and screw up. Use slow movements mostly.