Hi Angelos3000,
If you want to do the rust effect, what I usually do is to water brown ink down slightly, use a thin brush and apply it around the bolt, and then draw a rough triangle down from the bolt. Go over the triangle again, except leaving a small rim out, and keep doing to required darkness. What you should get is a triangle of high intensity rust near the bolt, fading out towards the bottom.
Hope that helps.
