Thereis a tattyshop/PSP filter to instantly add scanlines to an image but sadly I no longer have it nor can I remember who made it. Simple thing to do is make a big scanline layer then save it as a PSD for future pasting of the layer.
(
Pasanonic 's been known to cause insanity in laboratory mice,
Fri 17 Nov 2006, 12:35,
archived)