You have your work cut out for you. I tried to achieve this effect in bryce and tried volumetric spheres tried several things by converting the character into a volume material, transparent, boosting the luminosity. All looked pitiful. In Lightwave this is achievable with several methods but Bryce just is not that powerfull. So I ended up doing it all in post. The trick is to use subtle color acriations and boosting gamma and brightness values. Then a liberal dose of hands on painting to get the proper effect. This image took days to get the effect to where it is. And still it was not exactly what I wanted. Came close though.