Ironically, your happenstance with the vinegar is one of your best bets. Try heating it up and it should remove it faster. It is often used to clean paint brushes after paint has dried onto them. I'd personally bring the vinegar to HOT in a tea kettle or the like, lay down a bunch of old towels in the bathtub and then soak the towels with the hot vinegar. Let it sit for a while, remove the rags and then use a scouring pad. No clue how much of the paint it will remove, but if just scrubbing with a rag was getting paint off, I'd think this would get most all of it off.

Vinegar did not take off much of the paint, tried KOOF OFF it is not taking all of it off either Just around the rim of tub.

Next step paint stripper? If so what kind?

What kind of paint?

The typical tub paint is epoxy based, and methyl ethyl ketone (MEK) is the chemical that removes it.

It is a rather nasty solvent.

It does not dissolve the paint (like sugar dissolves in water) but chemical breaks it down.

There is NO actual solvent for cured epoxy.

I have no idea what kind of paint was used apparently it was not mixed well parts of the paint comes off very easy other parts I need a hammer an chisel I think LOL

I've been using a razor scrapper an it's very slow goin now that I seem to have most of the easy stuff off.

All the paint is off the outside of tub an around the rim an about 1/4 of the way down the sides. I'll tackle it again tommorrow.