Thanks guys
The weathering is just wet/dry brushing
first layer of dark brown / burnt sienna appled quite wet all over the tires and lower chassis working its way up the body work a bit . Then a drier brush with Earth tone over the dark brown ,I tend to work the brush in the direction of travel if that makes sense .Finally a very dry brush with a bone colour applied over the earth tone . Thats it really its all a bit slap dash and hap-hazard TBH .