it doesn't work. I am a cleaning product *****, and I still keep going back to a true 3 stage process.
The 3M line, or the CarBrite stuff. If you can't find those, the Meguiars 3 stage system has been proven time and time again.
The trick to black is take your time, and use clean rags. Wash, claybar, compound (depends on severity), Polish, Wax.