There is no “right” way to whiten teeth with activated charcoal. Koreans put it in their toothpaste, Crunchy Betty swishes with it, and some people simply brush it on straight. Personally, I prefer the following method:
Open a capsule (about 1/8 teaspoon) and pour about half into a cup.
Wet your toothbrush and dip it in the charcoal, then brush gently. Keep in mind that you are not trying to scrub your enamel, you are simply massaging the surface of your teeth with the activated charcoal so that it can attract tannins like a magnet.
After brushing, hold it in your mouth for 2-3 minutes to allow it to continue to work.
Spit and rinse thoroughly, then follow with a second brushing using your regular tooth powder/paste.
Now look in the mirror and smile. You may see a difference with the first application. If not, give it a few days to a week and I promise you will!
Source: www.thehealthyhomeeconomist.com