For really dirty paint I have had good luck with meguiars ultimate compound. Have not had to use it a long time because I don't let the paint get that dirty anymore. Many times after wash I go over the paint with a detail/wax spray and micro towels. I really like Jax Wax Hawaiian shine, I buy it by the gallon on Jegs, no tax and free ship. I basically don't use any paste wax anymore. The good detail wax is all that I need. I have a black Honda Ridgeline and it really pops with the Hawaiian shine.