Thanks for your words guys, I am glad you like the paint job.
So let me tell you about how I did it.
First of all, the result you see is not just Airbrush.
The colored panels, red squadron markings, and some weathering with Model Master's Burint Metal and Burnt Iron were applied with airbrush with the amount of Maskool needed here and there before airbrushing. Then, if the color of the panels looked too strong I downed it with the basic color grey used in the whole X-Wing.
After the Airbrushing is done, comes the most fun part of it, the acrylic water based paints to do some washes with brushes and something to dry and remove the extra paint to get the rust and dirt effect on the F-4 engines and where it looks it needs some color detail.
After the washes are looking good I start applying the weathering powders with brushes of different sizes, mostly the very dark burnt areas and some dirt and extreme rust retouches.
Finlay, some Dremel here and there to simulate some damage on the wings. To get this effect right, the X-Wing should be painted black before the X-Wing gray is applied, one of the reasons we cast the revisited X-Wing on black or dark grey resin.
Then comes the lacquer to seal it all and prevent the powder weathering to be removed by manipulation.
I hope this helps someone with the aging of his X-Wing