First, boil a large pot of water on the stove—the pot should be big enough to fill the sink with water. Pour 1/2 cup of dish soap (it doesn't have to be Dawn, but should be a soap that cuts grease) ...

Spray the tub surface generously with vinegar solution. Vinegar is a great all-purpose cleaner and can cut through soap scum and dirt and fight stains. Allow the vinegar solution to soak in the tub ...