why don't you do it in 2d.... maya glows suck ass... it's much easier in 2d (copy your image brighten it until your glow level is as you want it then blur it as much as you nee to to get the right amount of falloff, mix the original back on top... voila no re-rendering etc etc)
Alan
Technical Director - Framestore
Currently working on: Your Highness
IMDB