Answer: Metaphor used: "j-e-r-k-l-i-n-e Skinner"
Explanation: The metaphor used to describe "Slim " is "J-e-r-k-l-i-n-e Skinner". In the book, it describes Slim as a tall men with a crushed stetson hat, capable of driving ten, sixteen, even twenty mules with a single line to the leaders. He was a "J-e-r-k-l-i-n-e Skinner."