I have an old bathtub that will not stay cleaned no matter how much I clean it. Please tell me how to resurface an older bathtub. Thank You
You hire a company to do it. Not a DIY project.
You didn't say what type of tub you have?
If its cast iron or enameled steel it can be resurfaced, but as was mentioned by Handymac, it will require a professional service, it is not a DIY project.
If it is fiberglass you can use a power buffer and the fiberglass rubbing compound that they use to refinish boats and automobiles.
If its acrylic I haven't got a clue how to resurface or repair it.