Hey, welcome to the hobby & forum. Please do give us pictures of Georgie.
You can literally just put sphagnum moss on the top layer of substrate in the enclosure and it'll do the trick for you. Alternatively, but not as pretty, you could get a plastic pot with holes poked in the lid and fill it with sphagnum moss, or as you said, just put it over decorations, in their hide, etc. If it's going in with the substrate or over decorations (Georgie may drag it off the decorations) where you may not be easily able collect it when it's cleaning time, you'll probably just throw it away every time you clean the enclosure. But you can keep sphagnum moss for 2-3 months, perhaps sooner if it starts to smell real bad.
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