Attached Link: http://www.nerd3d.com/

You might also look at Nerd's "fog tool". It comes with layers, so getting a soft fluffy look with a lot of depth control is possible. He has a cloudtop addition to it. 10 bucks. "It comes with poses and maps for several Fog Effects, Haze, Mist, Rain and Snow." I snagged the picture from his store. I have the original, but the stuff in the upgrade is tempting.