ok i thought i would share this out, i have never seen a tutorial for it befor, but if there is there is no copying or idea stealing meant.
step 1: open a new document, anysize shape or form, just mke sure its in colour
step 2: make your backgroud, i'll be using this very basic backgroud using difference clouds and some downloaded brushes:

step 3: now for the actual tutorial, you'll want to reset your brushes to the default photoshop brushes. Find this brush:

step 4: set it to these settings:


step 5: now on a new layer at the top do somthing like the following (make sure your colour is set to white):

step 6: now go back to your brushes and choose a regular airbrush pixil sixe 9 or 13 make the settings the same as they where for the stars (you hould only have to click on shape dynamics and scattering for the settings to remain the same) then follow the brush stroke you just did with the stars to get somthing like this:

step 7: for the final step all you need to do is set the layer type to overlay and you should have a pritty good effect. after that just add a border and whatever to get your final result.
Heres what i got: