you don't use the image he posted. Except as referrence. You use a 1 px brush, and draw a bunch of scratches (black & white) and use that painted texture as a mask for a blurred version of what's behind the glass. (Don't ask me how to do that last part, just repeating Eric. Eric, explain that last part :P )
Ok I understand. And no... I cannot paint well... haha. So I decided to gather pictures of what inspired me. Probably should have done it sooner. This is taken from Halo 3 Campaign: Crow's Nest. I would try and draw something but it really wouldn't look how I would want it to. I took a look at something of the concept…