Northern Lights - How to animate them???

Up to the final few days of creating this animation for 2nd Year Unit X project, I was panicking about how to create the effect of northern lights in my animation. Certain things are good for creating an effect as a still image, for example brusho and bleach or wax resists, but they would not have the fluidity for a smooth animation. Both these techniques prove too unpredictable for a smooth, fluid motion.
In the end I turned to photoshop to create gently glowing lines which faded in and out using the frame animation timeline on Photoshop CC, this allowed me to keep control via the opacity levels, glow levels, colour intensity and spread. This technique alone was not enough though as it is too clinical and computer-generated for my taste and would not have sat well alongside the hand-drawn and puppetry elements. I combined it instead with layers of film I shot of watercolours swirling in a glass dish. This combination grounded the photoshopped animation, made it more tangible and gave it an elemental feel. The real footage also provided a natural movement that would have taken weeks (if not longer) to perfect.