Oh the great cast iron skillet.
Cat iron skillets are great to cook food with and I love mine but they do require special care.
Here's how I clean my cast iron skillet with salt.
First warm the skillet up on the stove and then take a cup of coarse Kosher salt and pour it into the cast iron skillet while it's still warm.
Then take a folded up kitchen towel to scour and clean the skillet and then after you've scoured the cast iron skillet throw the salt in the skillet away and rinse the skillet out with hot water and then dry the skillet immediately.
You can dry the cast iron skillet out with another kitchen towel or turn your stove on low heat and place the cast iron skillet on the stove to evaporate the water from the cast iron skillet.