How can I get my tub cleaned when it needs a gloss added?

A Magic Eraser will work well to clean the tub of any soap scum. Clean it well and dry it well and add a product called "Gel Gloss", available at most big box stores. It will make your tub shine like new....follow the product directions.

Try wet & forget shower. It is really good to clean without scrubbing. It will take a few weeks to get it clean, perhaps use 2x a week until you get the results you want. Then weekly to keep clean.

Rustoleum makes a paint kit for bathtubs

No quick fix. What has happened is that over the years, it has been unknowingly been cleaned with the wrong products and the original factory finish has worn off from incessant unnecessary scrubbing. Damage is done, can't be undone. You can try the wet and forget product previously suggested and see how that works out. Or you can have professionally reglazed. Or try one of the home kits.

Thank you Janice, Kathy, Morgan, and Naomie you have been very helpful!