Few ways of doing it...
you can duplicate the layer, blurry quite a lot and set the layer mode to 'screen' or 'lighten' or 'colour dodge' etc - each have different effects... creates a diffuse glow effect.. then erase in places...

As for my skyline i just added a light blue gradient fading out and played with the layer modes....
Looking at the bmw... looks like its just been brushed on with white

inb4 mainstream

Yeah J_HUI i use gradient maps alot too, they're the best!
To get a cool surreal blur you can duplicate you final image and use a gaussian blur with i high setting usually about 6-10 depending on the image and setting that layer to linear dodge or screen and lowering the opacity until you like it. Its the same tecnique i used on my Subaru chop.