Recently I had tested some dull-reflection materials using texture bump. The image is a glass version of it.
I used wooden bark texture for mapping roughness and normal on window plane.
The texture connects to the bump node. The bump node connects to Diffuse’s normal and Glossy’s normal.
The texture also connects to Glossy’s roughness through ColorRamp.
This normal and roughness is responsible for rain’s droplets and sweat on the window.
This is the covert texture behind which I used in image texture node.
As a decoration, I added glass sphere particle on the plane to be bigger rain drops. It’s like pimples so perhaps I should have made them more deformed shapes.
You can download the blend file from the Blend Swap page.