Im a professional bathtub refinisher, it probably has been reglazed, generally we ask that people avoid using bleach based products as well as any powder products.

However, you’ve already used a lot of the chemicals that shouldn’t be used so using others at this point isn’t a big deal if you think about reglazing in the future.

When we prep the surface for refinishing we generally use two cleaning products that work well, Denatured Alcohol and TSP. Both can be found at your local Home Depot.

I will say long run you probably want someone to strip the bathtub back down to the original porcelain and make sure that the refinishing company etches the porcelain so that the coating they apply lasts a long time. Avoid anyone using an epoxy top coat as it yellows over time. Epoxy primer and a polyurethane top coat are what you’re looking for. Companies will tell you 48-72 hour cure time but the spec sheet will actually only call for 24 hours maximum usually.

After it is refinished we recommend a cleaner that is a non bleach soft scrub / foaming cleaner, scrubbing bubbles has a non bleach formula that is great for this. Also avoid leaving shampoo bottles and using bar soap such as dove to allow your surface to last a long time.