I know there is a way to do Tevilas Ezra( and hence erev yom Kippur Tevilah) in the Shower how is it done?
The amount isn't 40 sa'ah, it's only 9 kav. From an IDF Q&A distributed by ShemaYisrael:
That means 9 kav is ~3--6 gallons. Even a low-flow showerhead will use that much water in a 5 minute shower; of course how much of that water wound up on you? Make it a ten-minute shower and I think you're all set. I don't think there's any other special procedure, other than making the shower continuous (not turning it off to get the soap or something).