I have an old tub (porcelain, I think) that I used to clean with Comet once a week to remove scum and build-up. But, I think that it has removed the finish on the tub, because the tub feels rough and grainy in places and I can't seem to get some dark spots out.
What can I use to:
1) Remove the dark, dirty spots?
2) Keep the tub clean without further damaging it?
Right now, refinishing the tub is not an option.
Thanks so much!