Besides being allergic to Aspirin , I have always had problems with Chlorine products giving me fits, setting off my allergies, and oh...what a headache I get.
So a long time ago I got far far away from Comet, Bleach, or anything one usually uses.
Bon Ami works very very well to clean both Fibeglass and Porcelan bath tubs, sinks and toliet. "Hasn't scratched yet" - is true. After I shower , I wipe off / squeegee the walls and such. Regular Isopropol Alcohol works well to clean as well.
I use Simple Green quite a bit as well. You will not believe what I use when I am out of Bon -Ami.
Baking Soda.
Yep, does a GREAT Job of cleaning , great for stainless sinks, tubs , toliets ...you name it. It too does not scratch or harm fiberglass or porcelan. Great thing is - it rinses off and leaves NO film.
I might spray with Simple Green , or ETOH , then shake some soda to sit. soak....light scrub, rinse off and done.
I like the simple and especially stuff that does not cost an arm and leg to use.
HTH