Cleaning Mildew Out of Electric Percolator?

In the coffee/tea business, we use crushed ice to clean out our glass coffee pots. We swirl the ice several times and within a minute or two all clean and any stains gone. Sometimes with a teeny bit of soap, sometimes not. Gets the stains out quick.
Today, I had two brown stained jars to clean but no crushed ice in my home. In 2012, I discovered that crushed glass did the same trick for soy milk stains.

Even for old stains. Depending on the amount of stain,it can take up to five or ten minutes of swirling. I put lids on and shook vigorously. These were old stains. All gone. Like new when held to the sun. Need to be careful when using glass rather than ice, of course.
I keep my glass in a jar ready for another use. Contrast colored glass other than the one you are cleaning would be ideal.