today at work i asked our garden specialist because i also picked up some sphagnum moss for my hermies. she said to go ahead and boil it for about 15min (you dont have to use treated water) and you are good to go. it will retail a lot of water so press the extra water out.
Let me know how it goes for you i havent done mine yet!
You don't need to boil moss. Just soak it in water, squeeze it out and place it in the tank. You can set it on the substrate or create a pit with a plastic bowl.
I wouldn't use the Spanish Moss. The sphagnum is fine.