You should set it as a pattern, just make a 5 by 5 pixel document, and draw a diagonal line to corner to corner, click Edit>Define Pattern. And name it Scanlines. To use it click, Edit>Fill and select it from the box.
I was looking at year sig in a different thread and I decided to try something liek yours. Then I looked down and there was the tut . Great tut by the way I loved it.