K.N.
Hi K.,
I hate having this problem too! I don't know of any good remedies, however, once you get it clean you should squeegee (sp) the door before getting out. It's not that much work and only takes a few seconds. It will eliminate getting the hard water stains that you spend hours trying to get rid of. I had the same problem at a house I used to live at until my neighbor enlightened me. I just leave the squeegee in the shower and run it over before getting out each time. I have even trained my husband to do it as well! I would definatly try the Mr. Clean eraser to remove the stains. I have heard wonders about those things.
Good Luck,
K.