Welcome to FSM je77er.
There are many ways to weather a vehicle. Some are dependent on how you want to depict the final model ie: just dusty or up to its waist in mud.
One of the techniques that is used by many is dry-brushing. This is used to highlight any raised details on your model. Load a large brush with paint, scrub the brush on a piece of cardboard until you see nothing more coming off of the brush, then brush the model until small amounts of paint adhere to the raised surfaces. Choose a colour from a lighter shade of the base coat to a silver. Do take your time with this technique, less is more until you get the feel for it.
For dusty looking vehicles, use earth tone pastel chalks. Grind the chalk sticks on a piece of sandpaper until you have a small amount of dust. Apply to the model with a brush with emphasis on the lower sections and flat surfaces where more dust builds up. Choose an earthtone pastel for the best results.
I don't use oil washes so I'll leave that to someone else's reply.
Hope this helps a bit.
Enjoy the forums !!!!!
Happy Modelling and God Bless
Robert