I wanted to give the mechanical arm an aged look, as if it had participated in multiple battles. For this, I created an effect of erosion in all parts supposed to be mechanical. Those effects are performed after regular lighting and shading. All of them are done with brush technique. Some of these effects could have been created with Maskol or similar products, but I prefer the brush method because although it is more complex and slow, it is more accurate. With it, I can control all the effects I want to achieve. It is simply a matter of choosing the right color tone taking into consideration the base tone of the piece we want to wear out. In this case, as the figure has mainly light colors I chose a mixture of Scorched brown by Citadel with Dark earth by Vallejo, which provides the perfect contrast. However, options for this kind of mixtures are almost endless. This technique requires patience, as it involves drawing small irregular marks, never rounded, with a very sharp paintbrush, not necessarily a small one. The small chipped traces must be completed with very thin lines that simulate scratches. It is really common that chipped painting, if not planned beforehand, has a regular general effect, as we tend to make all traces look similar. The key is to alternate their direction, size and shape. You have to take into account as well that these traces occur in contact areas and many times they will cover the shape of light we were planning on doing. To solve this, I apply a final layer of a very saturated tone before starting the erosion process. As a complement to chipped traces you can create rust effects such as stains or spurts in some areas. Smoke color by Vallejo is perfect for this purpose, because it provides a glossy touch simulating grease. Other tones close to Vermin Brown or Vomit Brown by Citadel also work perfectly well.