Personally i dont like the new washes. i prefer to water my paints down further and paint directly into recesses.
I have never done a tank myself yet, but i do know tamiya makes excellent weathering kits.
They are powders you brush on, then once you have brushed them on you use purity seal, so basically finish the painting of the tank and highlighting and shading then use tamiya. Or the new forgeworld powders look good even too.
Could chip the paint and paint black with silver edges, or silver chips, etc.