yes its going to be my traction tug for towing, want it looking really weathered...
Righto, are you nay good with an airbrush? Reason is, the rusting I used is a powder (pigments) and you use pigment fixer to dab and brush on, there are three different types on this model. It doesn't react too well to matt or gloss varnish, it just blends into one brown mess or goes a pinky colour. You can buy rust, various colours in acrylic paint (water based) that you can apply via airbrush or brush, if that is any help.
One great technique for a patchy surface is to use the salt method, really easy to do. If you want I can write this up for you too.