Best Way To Whiten Teeth! by Best Way To Whiten Teeth! Now I know that there's so many tooth pastes and mouth washes out there for whitening teeth but none of them really make much of a difference. With this particular toothpaste my teeth have gone 2 shades whiter in 2 uses.Use Luster NOW! 3 times a day. Make sure to brush for 5-6 minutes. Use a small amount because a little goes a long way with this. It contains peroxide in it. You can purchase the Luster NOW! Mouth wash as well or just use your regular mouth wash. Remember to floss! That's important.