The bridge over the river which you crossed to get to Quereño marks your arrival in Galicia.This is a curious town full of people who mean well but do not likely know the land outside of town. You enter town after passing over a bridge and under the train tracks and are immediately faced with a barrage of arrows pointing left, straight, and right. The arrows are all sorts of colors, and the locals will tell you that some are from a recent construction job in the area.
From Quereño, you have two choices: Sobradelo along the river, or a longer detour which takes you through Rubia. I walked back and forth through town talking to the same cast of characters numerous times before being tracked down by a young man on a bike whose grandfather knew the way to Sobradelo.
Nobody knew the way to Rubia, but everyone agreed that it would be a long mountain hike, likely in the opposite direction of the directions which follow.
To get to Sobradelo, you need to turn to your left twice. The first will a hard Left just after the train tracks you go under, and the second will be at the first street after that. It is a short distance until you get to a very ugly industrial building (actually the end of a canal and dam which feeds water into a hydroelectric station and the Rio Sil beneath your feet). Take the trail around the building and uphill. It is a pretty good climb here. Once you have begun the climb, keep to the left at the first two forks in the road, and right at the third. The train tracks are running through the tunnel that is beneath you. You will eventually find yourself on a gravel track which runs between a set of train tracks on your right and the River Sil on your left. It is this river which you will follow all the way to O Barco.