I'm not 100% sure what you're asking about, but I think I know now... hahah
The very light thin streakings of light and dark that are going from leading to trailing edge on the aircraft? (I have them on the fuselage too but the darkness of the lighting makes it tougher to see).
There are two ways of doing them, with slightly different results.
I'm using PS 7 so these instructions are specifically for that.
One way of doing it, is to pick up an add-on to PS called Eye Candy 4000. Inside there is a thing called HSB Noise. I create a new layer above the metal panel, and paint it the same as your metal color, load up the HSB Noise add-in, and set settings to
Hue: 25
Sat: 30
Bright: 30
Opacity: 100
Width: .25
height: .01
Smooth lumps and Seamless tile
If you want different effects, you can change any settings.
Then set the layer to Linear Light at 4-6% and you're good to go.
The cheaper (albeit far more difficult) way can be done directly in PS with no fancy addons or anything.
Make a new layer above your metal. Pick black as your paint color, and the paintbrush tool.
In the brushes window go to -
BRUSH TIP SHAPE
Diameter: 18
Angle: 0
Roundness: 15
Hardness: 0
Spacing: 300%
SCATTERING
Scatter: 100% DO NOT put a check on "both axes"
Count: 1
Count Jitter: 0%
COLOR DYNAMICS
Foreground/Backgroud: 0%
Hue: 0%
Saturation: 0%
Brightness: 100%
Purity: 0%
OTHER DYNAMICS
Opacity: 50%
Flow: 50%
Turn on Smoothing and Airbrush.
Once all that's done, pick the area you want to put the texture on , hold down the mouse button and go crazy =). BE FOREWARNED, this only works left to right and right to left (unless you change the angle listed above), so if you want up/down, you need to rotate after you are done.
Once you get it as thick or thin as you want, change the opacity to Linear Light 4-6%.
Both look very close, and at such low opacities, no one will even know the difference ;-)
Let me know if you try it out and have any trouble =)