Cleaning showers is my least favorite thing....
We live in a hard water area and it's nasty. When we had the house built, the designer wanted to put in those nice pretty glass doors on the showers. I knew that would be a nightmare with the mineralization in the water, so I said no. I went with a good old-fashioned shower liner that I could throw in the washing machine and bleach.
I still have to do the walls. The best advice I have is to do it frequently. If it never builds up it never becomes a big chore.