This shader is completely procedural, easy to setup and quick to render. It's so basic but it gives you the sense of real dust, adding to your props some realistic properties and richness.
It might be useful for environments like basements, storage rooms, etc.
I'll be proposing two different ways to create this shader.
The first version is probably better, in a way that looks more realistic, but render times are also higher.
The second one is more simple, less real but it renders way faster.
It is always a good idea to know how to setup both version, depending on your production needs so here we go.
This material has been created using a blend node that mixes two different shaders using a mask. You can use a procedural or bitmap masks.
The first shader in the mix is the one designed to create the surface properties of your asset. In this case is called "teapot". Very simple shader with some reflection properties.
The second shader in the mix is the one designed to be dust. It's a simple shader without any kind if reflection, just matte properties.
You can also add some procedural noise as bump map, to simulate dusty areas and make some differences against the teapot material.
As mask I'm using a towards/away falloff in z direction. Playing with the mix-curve you can control the behaviour of the mix.
In the white colour of the mask we can add some procedural noise to create variation.
The best way to adjust all the shader parameters is testing them one by one in different renders.