The BEST and FREE way to clean the lock & key is to go to your nearest Del Taco or Taco Bell & grab 3-4 packets of hot sauce.
The mild & medium work best because there are no seeds, like in the really hot hot sauces.
At home, put contents of two packets in a small tea size cup or a flat plate.
Then simply place the lock in the sauce. Leave for a few minutes & look at it. You can put it back in if its still not all shiny.
This will not hurt it at all & you will honestly be amazed at how shiny & clean your lock comes out..do the same with the key.
Then of course, rinse lightly under cool water & clean thoroughly.
Also, a toothbrush dipped into the sauce and used to scrub resistant stains will work too.
And if you have any dirty pennies you'd like to clean & have time for it, put them in the hot sauce...its the same principle. The hot sauce will clean & shine pennies also.
GREATEST method I've found & its free!!!! 😀