Happy accident

Halfords grey undercoat
Lifecolour brown
Vallejo Mech Rust Texture
Flory models sand
Vallejo rust pigment dusting.
I used to work in a narrow boat yard so there was a lot of raw unfinished steel and welding.
The welds were always shiny and the plate surface mottled and rusty.
Admittedly it wasn't third best Russian armour plate!