If there are still pieces of shed on the snake, I would get them off now by using the pillowcase trick. Put the snake and a damp towel in a pillowcase and put the pillowcase in the tank and let the snake chill out over night. I have NEVER had shed still on a snake after using that trick.
You might just invest in a moist hide if he has trouble even with good humidity. When the snake goes blue, up the humidity in a place where the snake likes to hide out. He's forced to be in a humid environment which will help the shedding process!
I will try the pillowcase trick and the moist hide. Only problem is, with the exception of the eyes, it's hard to tell when the blue cycle is, as the skin generally doesn't turn nearly as blue/gray as images I've seen suggest.