Hi,
I would also argue that this is an area where some AF can be applied. I have seen the primer red done a number of times in various modelling mag's over time and it looks convincing.
Looking at Schattenspartans pictures I would lean towards Stickpushers idea though.
The road wheels (probably the entire tank) in that picture have been repainted, looking at the drive sprockets and rubber elements those would have been worn clean of paint after only limited use.
And the track guide horns would have been rattling away between those road wheels with only one way for mud and dirt to escape - up.
That is obviously nothing more then my , as I said initially - go AF.
Good luck on your Nashorn!
Best Regards
Johan