My process, has been to render an alpha image of the highlights i want to have an aura.

I then create a selection in Photoshop based on that alpha, and copy and paste. This leaves me with the hightlight on a separate layer. Then I futz with the levels, blending mode, and outer glow layer effects untill I'm satisfied.

I'd like to know what other people's methods are for capturing this effect. -- Especially for animations.

Thanks,
Scott