Also see this this
tutorial for more information. -adlabs6
Here's what I do for WWII planes. I have a slightly different method for WWI and for planes that only get a few rivets here and there.
First off, start with a handy dandy plane with panel lines already set up
STEP 1
The first thing I do, because I like doing it this way, is to draw out paths using the pen tool where my rivet lines will be.

(skip
STEP 3 if you don't want to use paths)
STEP 2
Set your brush up. I use a one pixel hard edged brush and I set the spacing to whatever looks correct for the plane at hand.
STEP 3
Once you've got the right spacing and the brush set up, the color you want for your rivets and a new layer for the rivets to be painted on, go to the path window sub menu and select "Stroke Path..." You can also select 1 or more paths from a whole set and selectively stroke just what you want.
(I know it sounds funny, but get yer mind out of the gutter!!!

)
It'll ask what brush you want, in a pop up window, if you've already selected it, it'll show as the brush you'll stroke with. If not, select the brush you have just set up.
...And like magic, the rivets will just pop up!
STEP 3a
If you don't like paths or don't want to learn how to use them you can do the same by using the pen tool and the shift key to draw straight or diagonal lines, depending on when you hit the sift key. You can't, of course, draw circle rivets lines or curved rivets lines without a path. You'll have to arrange those by hand.