What I did in our old place was wet the surface of the shower and tub (not the glass though) and rubbed baking soda on, then let it set for awhile but not so long that it dried, then poured vinegar over and it worked great! I had to use an old toothbrush In some spots but it really worked well. For the glass I used scrubbing bubbles and it worked ok. In the new place I am trying to use a squeegee after showering to keep minerals from building up.