Mixing sphagnum moss with substrate?

[AndrewM1217]

After moving my spotted Python from a sterilite tub to a 15gal glass tank with a screen top, I'm having a little difficulty keeping up the humidity. I was considering mixing some moist sphagnum moss into the substrate to help retain some moisture. Also, I have Saran Wrap over one half of the lid, and I intend to get a sheet of plexiglass over the weekend to replace the plastic wrap.