Override all Material / Clay rendering look

I am looking for a fast way to easily override all materials in my level to a midtone grey. As you probably know in physical render engines which I usually work with these clay renderings are used get fast preview renderings for lighting setup.

For my project I want to use this specific look for several video sequences without having to change every single material. Here is an example of the look I going for: http://www.tonytextures.com/wp-content/uploads/2015/03/03_model-clay-render-sketchup_580.jpg
Ideally it would keep the bump and specular maps and just override all the color textures.

How can I achieve this effect in Unreal Engine?

Any ideas appreciated! Thanks a lot!

you can use console commands to switch viewmodes View Modes | Unreal Engine Documentation

Thanks a lot!
I guess I should have been a little more specific tho:

When I am in Detail Lightning mode and I render out a sequence the final images are still fully textured.
How can I achieve the same effect in my sequencer / renderings?

How can I render final images in (detail) Lighting view mode? Anyone?

Check this tut