This is not difficult
Soap scum is alkaline...
You need an acidic product to remove.
The only problem with using an acid on glass is.
1.You MUST work very quickly.If you can't work quick get a helper that can.
2.You need to neutralize the acid as you work.Neutralize acid with? guess? An Alkaline!! yay : )
3.What's acidic? and why do you need to be careful with acid? besides your own skin...
Lime Away is acidic as are lots of things, but this is one of the easiest to obtain so go for it.
Be careful with it because. It can eat holes in you, and if you leave it on just a tiny bit too long it will etch the beautiful glass door and damage permanently the door frame and hinges. Don't forget the shower drain. Keep the water running slowly in the shower so the shiny drain piece does not get damaged.
Wear Gloves you are not bionic
Start at the top, Work in a small section, WORK FAST! and keep a bottle of dawn or another dish liquid right beside you to neutralize the acid.
Rinse with LOTS OF water and the dawn as you go before starting with the next section
Use 2 separate buckets and do not use the acid sponge and the same sponge for neutralizing.That would be very dumb.
I can't tell you how to do this, not really, but this is what I did and it worked.I have to admit I did not use many chemicals from the grocery store. I'm suggesting this so that it's easy for you to get something that is obtainable.
Remember to work QUICK
Check out the entire door before you begin
The hinges, the frame, the drain, THE HANDLES that you will use to turn the water on and off, the glass.All those metal pieces including the glass will be affected by this.You can also scar the handles if you adjust the water with a glove that has acid on it.