I would soak longer than 30 minutes. If you have a plastic tub with some holes in it, or a deli-cup. Fill it with lukewarm water and add a few paper towels so the snake has something to grip. Make sure the water only comes up halfway on the snakes body.

I would try soaking for an hour.. but even a couple hours might be helpful to make the skin come of easily.

If you do use a pillowcase, make sure it has a LOW thread count. If the fibers are too tight, the water could fill in the gaps making the pillowcase airtight, which is bad.