When I think of Trollbloods, i don't think of big foundries filled with weapon and armor makers. I think of little stone smithies who are concerned with function over form. Their weapons and armor are made to last, and after a season of campaigning, the steel is dingy and weathered. Below is my process for making steel look old and beaten.
This process is not limited to Trollbloods, it would fit well in a Khador or Cygnar scheme.
Step 1: Basecoat the metal areas with Rhinox Hide.
Step 2: Using a junky brush, stipple Mournfang Brown around the metal.
Step 3: Using your junky brush again, stipple Thunderhawk Blue around the metal.
Step 4: Drybrush the entire area with Necron Compound.
4 easy steps to a battle worn army!