this is pretty big for the signatures and avatars section imo, but for blending, try moving the render layer back behind your other layers so that that line thing isnt so noticable, then paste new layers of the render on top and erase the outer edges away so just the focals remain, then work from there. or you could just smudge all edges and cover up the big messups on the render, or just pick better render, that shouldnt be a problem if you have a decent render to begin with. good luck.