Excellent advice. I had done something very similiar with great results.
If he's deydrated, high humidity and having water available for him is the best thing. If you are still concerned, I would contact a good reptile vet. I
'm not a believer in soaking for rehydration (or anything for that matter). Think about people... if we get dehydrated, we drink a lot of fluids. Sitting in a bathtub isn't all that much help. Animals aren't a whole lot different. I'm not a vet, nor do I have years of experience. This is just my own beliefs from what I have read from many many threads and articles about it. Soaking can remove and break down the naturual oils the snakes body creates and releases into it's skin.