To create the appearance of a lowered waterline with rust and corroded metal, we used a Dremel rotary tool with two different bits from a sanding/grinding set. To replicate this effect, do the following: use a #953 Aluminum Oxide Grinding Stone at the lowest speed setting and gently grind the plastic down in a swath that measure somewhere between 1/4-1/2" high. A variation in height is a good thing to make the final result much more natural in appearance. Then, with a #530 Stainless Steel Brush, rub out the deepest gouges. Use very little pressure and let the brush tool do all the work. You'll be surprised how much plastic the brush tool can remove if you're not careful with the pressure you apply.

Below are examples of the effect the Dremel tool has on the plastic kit. When you apply a very fine sand or dust to this texture and then follow up with a good rust colour, you should end up with a convincing rusty surface. If you don't mind going outside your range of Citadel Colour paints, try a product called RUSTALL Weathering System. One of the bottles that comes packaged with this product contains a liquid "rust." You use it much like a wash – the more layers you apply, the rustier your vehicles will end up. Just Google the word RUSTALL and learn all about it.