Hi dadfad
I have found there are plenty of different ways of weathering aircraft, so the method you choose will depend on what works best for you.
I've done a few F-14's so I'll tell you how I did mine.
(low-vis scheme.)
I. Get the grey colours onto your model.(Light/dark Navy ghost gray I think it is.)
If you are painting a black cowl area around the cockpit,do that bit too.
2. Now the tricky bit[:0]! Study some pics of the paint scheme you want. (Home of M.A.T.S. is an excellent resource for F-14 data. I'll give you the address later.)
You'll notice the blotchy appearance of the aircraft, The best way I've found of copying this effect is to take the gray colour for the upper surfaces and use it to mix sublte darker(add a drop of very dark grey) and lighter (add a drop of white) shades. You can use the lighter shades on areas of the rear quarter and wings to show where new paint has been used to "touch up" those areas
and the darker shade can be used around panels (such as the boarding access panels, gun panels) where there is more wear and tear.When you finish blotching seal it in with a good gloss coat.
This can be quite time consuming but the result should be worth it
For the panel lines and other surface details I use a wash of kiddies waterpaint. I paint one section at a time and leave to dry for approx. ten mins.
Then I take a damp peice of kitchen roll and wipe the excess away. This leaves a very nice "used look" to the painted surface.
The web address for Home of M.A.T.S. is: www.anft.net/f-14/
Sorry to ramble on a bit there, I hope this helps.
Good luck!
Darren