No mystery to it. Here is exactly what happens from the moment you call to the moment we hand the job back.
The tub is identified as cast iron, steel, fiberglass or acrylic, and checked for previous refinishing, rust-through, and flex in the floor of the tub. That determines the whole approach.
The room is masked, exhaust is set up, and old caulk, trim and any failed prior coating are removed. Stripping a previous refinish is the longest part of the job when it applies.
Chips and cracks are filled and faired flush, then the whole surface is chemically etched or abraded so the primer can bond to what is otherwise a deliberately slick glaze.
Bonding primer first, then several thin coats sprayed with flash time between. Thin coats matter: a heavy coat sags at the tub radius and stays soft underneath.
Hardware is reinstalled and fresh caulk applied after the coating sets. Water contact usually waits 24 to 72 hours depending on the system used.
None of this is required — it just makes the visit quicker.