Should I brush my teeth before using Crest Whitestrips?

I got a couple packets from a friend, and don't have the directions. My teeth aren't grimy, but are the strips more effective after the teeth have been recently brushed?Should I brush my teeth before using Crest Whitestrips?
rinse your mouth instead of brushing your teeth because when you brush your teeth the white strips don't work. This is because the toothpaste blocks anything that tries to whiten your teeth.