A good shed should be finished in less than an hour if your humidity is correct. What are you using to measure humidity?
If you have a bad shed place the snake in a tall sterilite container, with a secure lid, and with just enough water to cover the body of the snake for 45 minutes to an hour. Then take a damp hand towel and let him run through it.
It is safe to assist a snake to shed. Just be sure, while letting him slip through the towel that you let him slip the shed off at his pace, and not pull it off, which could pull some scales loose.
I even have an adult normal male that will rub his head in our palm until he has the shed loose from both the top and bottom part of his head, and then completely shed in our hands. He has done this twice. Our guess is he must be that comfortable with us.