My question is though, whats the correct way of holding the moss down. Should I REALLY tightly tie it down with the threads being very close to each other or should it be more loose and spread out?
the more moss fronds are pressed right up against the wood, the better it
will ultimately attach as growing fronds embed themselves into the wood.
so, more thread closer together like a mesh, but no need to be very tight.
don't fret if your tied up moss looks like a flat mass dead against the wood.
trust me, in 2-3 Months when it fills in, you'll be glad you started this way.