Trailer36,
Welcome to the forum...
I agree with Bill.
My personal track technique involves almost all water based mediums. I first spray them with pain ol flat black paint as a preshade. I'll then give them a light overspray of a dark rusty brown with an airbrush. I used to use washes and drybrushing but on the last kit I tried something new. I took some pastel chalks and mixed them to a nice dirty color. I mixed some water, rubbing alchol and a bit of window cleaner with the pastels to make a wash. It takes some experimentaion and the effect isn't realized until its completely dry but It worked very very well for making dusty dirty tracks. As a last step I used a graphite pencile and a blending stump to create the bare steel areas where the road wheels contact the tracks. and the guide horns.
I am not sure what effect you are going for on the rusty hull. Explain your idea more and we'll see if we can answer more clearly... Is it supposed to be just really beat up or burnt and rusted...?????