First, Think of why the snake sheds its skin. They do so, to allow for further growth and to remove parasites that may have attached to their old skin, And to allow the snake to fully grow. 
 
Now a Witch would interpret this and use this energy to:
+ Banish unwanted entities
+ To heal
+ To bring growth, And change to a situation. 
+ Think “Out with the Old, In with the new” 
 
Snakes are also known to be very protective, Sly, And feared. So for these reason Witch would use the skin to bring:
+ Protection
+ Transformation
+ Strength
+ Jinxes
+ Curses and crossings
 
In Hoodoo practices the skin of a snake can be used to bring good and bad things. On the light side it is used to bring luck, break crossings (hexes) wisdom,  protection, and good fortune especially to Gamblers. And on the darker side it used to hex. To confuse an enemy, to harm them, or to bring rotten luck.