there was a recent thread on here about this. It said to heat vinegar, mix it 1:1 with blue dawn dish detergent in a spray bottle, spray it on, let it sit for hours, then brush while rinsing. I tried it and it works wonders. However, my dawn is concentrated and was crazy bubbly! So get regular, not concentrated. Since then or maybe in the same thread I read to use a Magic Eraser. Sure enough, I bought the heavy duty version and I wipe the shower down when done showering. That keeps it clean. Now I have one in the tub too. Before that I always squeegeed the shower. Now I just "dry" it with the Magic Eraser and squeeze and rinse the eraser as needed. My shower is white tile with white grout and a plastic pan.