Prepare the necessary materials.
However, this is entirely optional.
Then squirt the mixture down all over the sink.

Image credit: An Old School Home on Youtube
Allow it to sit for approximately 10 minutes.
Using the toothbrush, begin scrubbing immediately after that.
You will begin to notice the difference after a while.

Slowly but steadily, your sink will begin to shine.
Allow it to sit for a few minutes.
Then, using the toothbrush, clean the inside borders of the sink that are particularly difficult to clean.
