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).
The "9 kav" requirement allows for water that sat in a storage tank, too (unlike the 40-sa'ah-of-fresh-water for a mikvah). Which means the water can be heated.