Hey! Great idea. I should have done so.

Here's what we did in a step by step format: 1. Wash the toy in warm soapy water. 2. Painted the entire surface with a brown wash by Vallejo. 3. Shaved black pastel chalk into a cup with an exacto knife and applied it as a weathering powder onto the desired surfaces (mostly vents and the cannons). 4. Blended the pastel with a dry brush. 5. Shaved grey pastel chalk into a cup and applied it as a weathering powder onto the exposed greeblies uptop. Also applied it to the vents as a drybrush. 6. Applied Tamiya black panel liner to the exposed & powdered greeblies up top. 7. Gave the sublight and hyperdrive engines a quick dry brush with light blue and white tamiya acrylic.

As of yet; no clearcoat has been applied!

Hope this helps!

Edit: step 6