This is a phrase originated from Dead Run by Erica Spindler. Hereunder is the context in the book that I googled.
Rick’s Island Hideaway was the quintessential Key West bar: Jimmy Buffet on the sound system; killer frozen margaritas; a friendly clientele whose attire never veered far from shorts and Hawaiian-print shirts; walls hung with maritime paraphernalia, including a stuffed sailfish and a signed photo of Key West’s most famous onetime resident, Ernest Hemingway. It was the same photo that could be found in about ninety percent of the Duval Street drinking establishments.
And last but certainly not least,a bartender who could charm the skin off a snake.
What does "charm the skin off a snake" mean exactly? And how to use the phrase nowadays?