If yr shooting raw, just use the eye dropper in LR and select a neutral colour like a asphalt road or gray surface. I usually increase the WB a little, I prefer warmer images. Then set the black and white points so the histogram touches the end...
Interesting. As a photographer, it is important to set WB in the visual spectrum even when using raw capture. By not setting WB you are liable to clip a single colour channel so that when you make colour corrections in post, you will end up with...