Hey Todd:
You could also draw them on with either a mechanical pencil or a fine line permanent marker. If you do a search in this forum for "panel lines" you should come up with a pic by a guy who did a Rafale and used a grey fine line design marker to do the panel lines. It looked pretty good in the photo. He also did rivets, which are pretty easy to do with the same color pen if you use the Top Flite panel line template.
Hope that helps.
Antony
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P.S. -- I dug the link up for you Todd, here it is
http://rcuniverse.com/attachment.php?postid=159737