Welcome to your new shader,

Now you have an extra weapon in your arsenal of photorealistic tools!

The node group hacks into Cycles lightpaths to override the physical response of reflection curves  

The shader is pretty easy to use, the complex stuff has been hidden in the container, there is no need for you to tweak settings inside of it (but we' ll cover it later)

Starting Setup

In its basic state, you can set Colour, Specular and Glossiness using their relative sliders. To use textures, you can load the four standard maps, connecting the textures output to the Color Inputs, which are clearly labeled. If you plan to use a Normal Map, first unwrap your model then connect the Normal input. In its "neutral" state (for a Normal Map, that is) it has a defalut colour which doesn't affect geometry

You can create amazing materials only setting the parameters with sliders. However, using textures map you can get a greater variety and create details and dirt maps; the workflow is the standard PBR specular-glossiness. The sliders still control the overall strength of the effect, even with textures plugged. You can also use color ramps and MixRGB nodes, as per usual

Typical SetupRemember to set every texture as "Non Color Data" for colorspace

If you plug a Normal Map before unwrapping your model, or if you plug it and unplug it, Blender will create a fake UVMap or try to read info that is no longer stored in the node group - to avoid artifacts, just tab into the container -

...And delete the fake or unneeded UVMap

Thats' it! Have fun creating amazing renders!