While I was on the bus, there was a programme shown about the best way to shave. Various Chinese people shaved using electric shavers, shaving cream with regular razor blades, and some used specific brands of toothpaste in place of shaving cream. The best shave as well as the fastest? 黑人牙膏 (Darlie Toothpaste, formerly with the English name "Blackman toothpaste"). I had wondered what they could have meant when they stated the toothpaste was double action. Now I know at least one possibility.
I decided to look this up in English, and found some people that had tried it. It seems possible, depending on the toothpaste. Some might not feel so great – I’d bet that would include the lemon tea flavoured Crest I am using at the moment. I have some Darlie in my Korean apartment, so I already know what I will do when I get back.