I'm Covering Up the Lines

OK, I have been using a tutorial to try and repaint a plane for the first time. It says to start by making the window stripe and I did that but I find myself covering up the seams of the plane. Do I have to make a layer of the seams and rivits and all that stuff (if so how) or can I simply make them show through the stripe on the plane? Here's the page of the tutorial I'm refering too, about a third of the way down it describes how to make the window stripe-how do I make it so all the seams show through?
http://www.calclassic.com/repaint2.htm
Thanks
http://www.calclassic.com/repaint2.htm
Thanks