IMHO the article linked in the first post is incomplete and misleading. The proper way to use tint as WB control is this - click on tint operator colour swatch (not the colour picker), in the colour selector window, make sure that original colour is full white, if it's not, then reset it to the white first, then with inverse picker pick a colour from area that needs to be neutral grey and lastly move the value slider in the HSV full to the right. That's it, now you have set custom WB, which is not automatic, contrary to the claim in aforementioned article.
By the way, i recommend to choose 3 by 3, or 5 by 5 sample size, otherwise you risk to sample noisy pixel and set inaccurate WB.