So, just thought I'd give this one a bit more publicity. And so far I only got one covering dark metal, might do more later. We'll see
It's a method I recently discovered and started using after having tired of the cloud and sponge filter not giving satisfying enough results. And I do recommend it. It's a very good base to work from and add details to. However, this one's mainly considered for people using Doylle's shader.
It could be used with a different shader per see, but you will have to tweak your maps towards that shader in order to achieve the same results.
Cheers!