How do you know you brush well?

Here is a true conversation I had with one of my boys today:
Mom- "Son, did you brush your teeth?"
Son- "Yep."
Mom- "Did you brush them well?"
Son- "Yep, I even used toothpaste."
Gross. So sad and so true. Needless to say, tonight I will have a little better eye on the teeth brushing with my children.