This is a method for painting a weathered, dirty yellow. I use it for my Imperial Fists, as I want them to look like they've been in a war zone for quite a while. It involves a lot of steps, but each is fairly simple. It does take some time though, but I don't mind that.
HOW TO DO IT:
1: Spray the model with Averland Sunset Spray.
2: Put Seraphim Sepia Shade all over the model. I thin it down a bit with water, and give the figure two coats.
The result will be a yellowish-brown model.
4: Then it's time to build up the yellow. For this, I thin down Averland Sunset A LOT (it should be like milk). I then paint the model, except where I want dark shadows or really dirty areas. When that coat is dry, I apply a new thin coat, but this time a bit INSIDE the area I just painted. The transition between the thin layers will make it look like a gradient, when seen from a distance. The method can be illustrated in this way:
5: After that, I repeat step 4 but with Yriel Yellow (inside the previously painted area)
And then step 4 again, but with Flash Gitz Yellow (again inside the previously painted area). You can make the transition from dark to light colors as slow or fast as you want, it's all about taste.
6: If you want some very bright edges and highlights, I recommend Dorn Yellow.
7: If a transition between two areas look a but sharp, a glaze or two of Lamenters Yellow will help soften it.