Brushing is just like usual, although with the black foam. The tough bit comes when it’s time to rinse. After a while I gave up trying to water-brush the black foam away and resorted to three very vigorous rinses with big gulps of water – even then, I was still spitting black bits into the sink. Make sure you take time after you brush to check your face and lips for errant marks, too. And be a good housemate and rinse the sink out afterwards – white toothpaste stains on your bathroom sink are just about forgivable; charcoal toothpaste stains are not.