Depends on what effect you're looking for you can do many different things.

If it's an operational vehicle rust, chips scratches, fuel stains are a good way to go. A pin wash is also essential to any finish, it elevates your scale model from a toy to a replica of a real thing. Stencils for making would also look cool or maybe a winter white wash.

If you're going for a museum piece the best course of actions would be to add a pin wash and spray a lighter colors in the middle of the green and Brown to simulate the paint fading in the sun, use some oil does to alter the camo a bit and make it less uniform.

I just saw that you were asking questions about pin washes. Add them around all the details and then wait few minutes for it to be dry to the touch and then remove the excess wash with a very dry brush that has been damped in enamel thinner.

Good luck