Well my thinking was to keep it cheap and simple.
Its why I mentioned Spraycans.
Red oxide is just the color of the primer sealer, comes in grey also.
But way back when they used red oxide more.
Do you have the product Rust Oleum?
Use this or something close to it in the red oxide color.
If it is a lacquer product you can put any type product over it . just dont use an Enamel base red oxide product and put lacquer paint over the top of it or it will lift and cause all sorts of problems!!!

I would spray down 3-4 coats of the red oxide down , let dry good for a week to get hard , Then spray down 2-4 coats of color (your choice) . let it dry good. then use a grey or red Scotch bright pad wet with water and lightly scuff areas like top areas will fade faster the sides so rub more color off the tops till it starts to wear through.
You might get an old door and trial and error it , to achieve the look your after.
If you practice the technique enough , you will I think GET THE LOOK you are after.
while your out and about look around for old fadded out cars and really look at the look of how the tops and sides all look . Study it , I mean really look how nature does it.

Just make sure the paint products you use are all the same for compatiability.

SprayTEch