Put your snake in a sterilite tub with a couple inches of lukewarm water and secure the top. Leave it in there for about 30 minutes. When you take it out let it run through a wet wash cloth several times until the shed gently peels off. (this always works for me)
Or, get a pillowcase wet and wring it out. Place your snake inside the pillowcase, tie it off, and leave it for about 30 minutes. The shed will usually rub off while it moves around.