OK erm..
Try following this tutorial..
http://www.avivadirectory.com/photos...udge-tutorial/
Don't smudge the gun though like it would suggest to do so in the tut, just stick with the colours on the guy. See how that looks. Keep smudging out and it should fill the canvas.
If you have any problems with that, get back to me and I'll try and explain it myself, I think a slight smudge might work with this sig.