Well... I'm pretty impatient with incomplete sheds. Whenever Jacks had a bad one, after he had gotten off everything he could the first time around, I just put him on a shallow tub of water with a rough clean dishtowel. He typically finished it himself that way. Only once I had to to anything more, and I just made a tube with the towel and let him crawl through it.
I always did it as soon as I noticed his shed wasn't complete.