What tool do you use to clean BETWEEN glass shower doors where soap, shampoo and shaving cream get caught?
If they are standard shower doors, they should lift out and I just used a 8/1.00 toothbrush and some dollar tree spray foam. They have holes in the sides so they drain back into the tub, so if you want you can get down and dirty with some soapy water and it won't leak out on the floor side.
The nylon scrubbies they sell at that DT sometimes can be custom cut to the width of the groove and the you can "yarf" on it with a screwdriver, if it's really bad. Good Luck
Use CLR and use a drinking glass cleaner for your kitchen. The kind with the plastic handle and soft sponge head. This fits nicely between the doors and the CLR works magic
I like Ed Fred for built up minterals from the water.
Baby bottle brush/nipple brush. I clean homes and have found that the old fashion baby bottle/nipple brushes work best. I spray the cleaner and bush, all that old goo is gone.