I would have reservations about using the Krylon "Fusion" product on a shower or tub as its high gloss might lead to excess slipperiness. There are a number of two-part epoxies that can be utilized for the ABS and fiberglass elements found in the bath fixtures in your Airstream. The difficulty can be in identifying them - - a knowledgeable Airstream dealer or customer support at Airstream may be able to clarify what was used in each. The professional who redid my bath fixtures was able to identify the products by testing with various chemicals that he had. For the bath, he had to use three different primer/surfacers as well as three different top coats due to the three different kinds of plastics and fiberglass found in my '64 Overlander.
So far, after the first two trips, the refinished bath is absolutely delightful. A photo of the before is below:
The after photo is below:
Good luck with your refinishing project!