Well this is my first tutorial. I looked for the glow creating tut, but I couldn't find one, so I made my own. This is what I came out with:
First take whatever render you want. I used the cloak in my sig that I cut out with paths.
Make a new layer other then your render. Ok now we need to make sure you have the path around it a selection. Invert the selection by going to select--->invert. Then fill the background with white. Go back to the selection around the render and do a gaussian blur on the selection. You will have to mess around with the blur amount for the different sizes. Do a select---> feather on it. Once agian mess with the settings until right.Now invert the selection again and delete the background. Then open up a background and paste your new image into it. It should have a sort of glow. I hope it works, if you have a problem please tell me about it I may have forgotten a step.