Since soap scum is the junk left behind when the water evaporations, using Rain-x on your glass shower doors seems to slow down the rate at which that yucky soap scum can build up.
One bottle of the Rain-x pictured should last about a bazillion years (give or take a few!) if you only use it on your shower doors. That means it’s relatively inexpensive.
Rain-x is also super easy to apply. Here’s how:
Spray the Rain-x on your glass shower doors. It should only take a few squirts to cover the enter door.
Wipe with a clean towel cover the entire door with Rain-x and continue until completely dry.