Earthing the Brain is the process of cleaning your brain from past knowledge and experiences and thoughts that you have acquired and instead open your mind to unlimited possibilities without projecting actions on these past experiences.
This is not easy to accomplish. Our experiences basically defines who we are and its difficult to let go of what we are. However, looking at the world with an "Earthed" brain open our eyes to totally new experiences. An Earthed brain can listen more and see more.
You can say an Earthed brain is an application of Zen brain, an empty brain that can accept new knowledge, new experiences. Just like a brain of a kid that never fears to try new things.
An Earthed brain can make us see clearly potential Black Swans and sorta "predict" the unpredictable.
The most important thing, it makes us realize how little we know about the World, thus it teaches us how to listen and learn the most from our surroundings. Basically it makes us climb the mountain of Knowledge higher, except that the 'Ego' dog will cease to follow us up to the mountain.