Gosh, I just typed a load of stuff but my typing has disappeared. In essence, the following info is from an earlier thread,. Seems like an economical way to get to Sarria. I was recently in the bus station and it is fairly easy to find your desk, and people are helpful. Might be an idea if you have no Spanish to print on a card what you want - ie, Bus a Lugo/ Sarria, and that way you might save time! Wishing you the best. By the way, Monbus don’t really do booking ahead. It is like a normal service route rather than a long distance route.
VJS
Check out the timetables I’ve attached the links below
http://www.empresafreire.com. - service provides bus from Santiago Airport to Lugo
http://www.monbus.es - provide service from Lugo to Sarria.