So you're saying tie the moss to the mesh?
If you're using the plastic gutter guard, then yes.
First reason, it bends and doesn't stay straight or flat, so the moss would just fall down, but for the price ($5 for 20 foot long and 6 inches wide), it's worth the inconvenience.
I also realized that making a sandwich with the mesh wasn't necessary and it actually made it harder to fix patches. (i was using zip ties)
My second attempt, I instead of making a sandwich I just used one layer and used sowing thread with a bobby pin to weave the moss down.
This method was easier and the moss grew faster since there were more light shining on it.
The sowing thread would eventually break down over time, but before it even comes close to breaking, the moss would attach itself to the back of the mesh, so that's nothing to worry about.