At this point I'd give an assisted shed.

Soak them in a container or tub in luke warm water for 20-30m.
Use your hands or a washcloth and gently grasp around the snake, allowing them to tightly crawl through it. The skin should slowly slide off as they work their way through your hands.

In my experiences they actually seem to understand what you're doing. They are eager to contract their body back and forth through my hands to get their skin off.

Be careful though, it should be peeled back slowly, not fast.