Cool the pot completely before attempting to clean it.
Fill the bottom of the stock pot with hydrogen peroxide.
Put the pot on a burner and heat on medium until the hydrogen peroxide gets hot. Watch it carefully, and turn off the heat before the hydrogen peroxide starts to boil. Fumes from boiling hydrogen peroxide are unhealthy to inhale.
Leave the pot on the burner until the pot has completely cooled.
Move the pot to a sink, pour the contents into the sink and wipe the inside with a soft cloth.
Dry the outside of the pot.
Repeat steps 2 to 6 as needed to clean the inside of the pot. Usually the inside will be clean after the first time.
Scour the outside of the pot with the scrubbing pad and the powdered cleanser under warm running water.
Wash the whole pot inside and out with hot soapy water, and then rinse it with clean water. Dry with a dish towel.