Weathering/Distressing Something Rather Large

[TorqueVR]

I'm not sure is this belongs on this group but I'm sure that someone will have the answer. I have a Toylander Jeep first built for my grandson 15 years ago which has been gathering dust in the back of the garage for most of that time but as I now have another 4 years old grandson his dad and I have resurrected it. We've added a mortar to the trailer that shoots tennis balls and then we added our interpretation of a 0.5 Browning. We then "got the bug" and added .303 and Vickers Lewis guns (made by Sarik Hobbies who make RC planes, boats and associated bits and pieces) , which is where we are now.



What we want to do is to repaint it and add additional kit to make it into an LRDG or SAS desert jeep rather like this


Spray painting it will give a near perfect finish but we want to weather it make it look a bit beaten up and rusty. That's the bit we don't know how to do and should be grateful for some advice and guidance.