Shower scum remover - cup hot vinegar and cup Dawn dishwashing liquid. Shake gently and spray. Vinegar should be warm so it doesn't work as well to mix in advance. Another recipe is 1 part parts vinegar and no need to warm
OH, NEAT! How to keep your Shower clean with Rain X. that is something that I never thought of. but it works on cars so why not other glass surfaces too? I could put it on the window above the sink that gets splashes as well.