The problem with substrate and humidity... the dirtier the better. The two best nice looking substrates are the coconut husk and cypress mulch. Coconut husk is the most dirtiest but it does a better job holding humidity then cypress mulch but cypress mulch does okay if sprayed at least once a week. The biggest issue with soaking the substrate for humidity purposes is if you keep the snake on constant wet substrate you are risking scale rot. The best healthy way of adding humidity (IMO) is providing a humid hide or getting a humidifier. Providing a humid hide Or section using either moss or coconut husk, placing it on the hot spot of the cage (make sure the snake has somewhere to cuddle up on the heat pad) will provide humidity through out the cage, give your snake a place to curl up to for extra humidity, and will leave out the risks of scale rot. My snakes are in tubs and humidity in my area is naturally around 50-60% but when they are in shed, I soak some coconut husk in a tupperware container and set it inside the tub on the hotspot to create extra humidity. Works like a charm and I can continue to use the newspaper and avoid the dirtiness of the coconut husk itself.