In the aquarium hobby we do this fairly easy by chopping up moss or even sticking it into a blender. Add a little bit of spagnum moss (this is optional,some say the moss will retain more water due to the spagnum) and add some water so you end up with a smearable substance. Note that some add buttermilk instead of water as it's said to give extra nutrients to the moss. However some also noted that this might increase the risk of mold. Personally I'd just stick with the water as I've had good results with that.
Now that you've chopped up/blended your precious moss with the spagnum and water you're ready to smear it onto any hardscape you want. Rocks, wood, background etc. The moss will attach and needs to be kept moist and plenty of light. Not too wet as you might spray off the moss before it had a chance to attach. Give it a few weeks time and you'll have a lush background of moss that has grown in naturally without the use of any silicone or superglue.