As the desctiption says: This is a plain written guide for those, who like to go on a scavenger hunt for themselfs but might be frustrated because everything looks so similar. The level is completly blue and even with screenshots or a video you can't really make out the exact location most of the time anyway. So no screenshots or videos are going to be linked in here :)

To make a few aspects clear: You need all the 28 spirits to do a greeting animation that looks kind of like praying. Go close to them and see, if they do the animation, otherwise take a few steps back out of their "trigger"-radius and then enter it again. In the groups this is kind of tricky, but each of them has this animation.

If you get lost, try to find a fox statue. If you bark at them, their light will show you the way to the next zone/part of the level and you can backtrack from there.

If you can't find a spirit but are kind of sure you are in the right area, stick around for a minute or two. Some of them tend to spawn in a bit late or are on a circular route and may come around to your location.

The progress you made during your first walkthrough is also safed. So if haven't found all during your main game, just re-enter the level through the main menu and hunt down the ones you might have missed.

Now to the start of the guide:

First you have to follow the red orb through the first big area of the level. Nothing fancy to collect here, so just grab a "spirit flower", walk up the ramp, jump over the big gap in the rocks with the spirit dash and follow the river into the gap in the rocks. At the intersection turn right and then left into the first bigger area of the level.

When you leave the small ravine, directly turn right and follow the river through the forest.
The first spirit is walking around in the woods quite close already, so make sure to stop and look around.
Two more are all the way back near the big waterfall at a small forge. Now turn around and go back to the exit of the ravine and cross the river straight (or just cross the river at the forge and follow it back on the other riverside until you meet the path again).
The next spirit is walking up and down on the path there and this one you most likely already saw when you followed the light from the first fox statues. Now just follow the path to the second area.

You now have two options: Follow the path or turn left through the hollowed tree. First we are going to follow the path to enter a cave like area with a fox statue in it - and a spirit is directly in front of it.
Now follow the path further, turn right at the intersection and when the path comes close to the rocky border of the map, just wait, follow the path or make a sharp right turn. One spirit should run around in a bigger circle here, so just make sure to stay around the area and he will come around.
Now back to the second option: Follow the path through the hollowed tree and you will see a fox statue on a rock. One spirit is running a circle here, so you can follow him to the right or meet him when you take the left path and then right around the rocks.
Now follow the left border of the map and you will come across another hollowed tree bridge. One spirit is running around the entrance on the side of the tree you are coming from. Otherwise just cross the brige through the tree and keep your eyes open.
The last one of this area is also nearly unmissable, because it is directly on our route to the next area, walking around on a path shortly before you see the "spirit keep"-waterfall for the first time.

At the waterfall you have the option to turn left or right. First turn left here and make sure to jump up the rocks to a higher plateau, where one of the spirits is meditating.
Now go back to the waterfall and follow the right path through some rocks and an arch. One is now sitting in front of a small house on the right. Now turn left and another spirit is in his house there.
Turn around again and follow the path upwards. One spirit is running around on the plateau and the wall here but turn right first. We will be back in a second. You enter a smaller woodland area, where one spirit is running around on your way into the area and one is sitting in front of a fox statue further in the back. You can take the jumping portal from the house here to go back to the area we just came from and follow the upward path again (or take the staircase in the tower for variation) to collect the sprit running around the plateau there, then follow the wall on the left. Make sure to jump on the bricks around the tower first, because one spirit is hiding on a ledge here. You might see him, when you take the jumping portal, but it's one of the easiest to miss. Now enter the tower and spiral upwards.

You enter the bigger courtyard of the keep and have three options here. Left around the tower, right around the tower or downward between two fox statues to the last area of this guide.
The first spirit is running around the big tower here in front of you, so make sure to circle it until you find him.
While you do this you might come across the three spirits (on the right from the start) near a tree and a fountain. Make sure they are all "greeting" you as well.
In the middle of this yard is a glowing fox statue. Directly infront of it is a small house with a spirit inside and if you exit the building and go straight across the yard there is another one in the house there.
Now take the small staircase you saw while crossing the yard and take the stairs down in the tower on the left, to go to a lower courtyard. There is also one spirit here. Then go back up to the start and follow the path down between the fox statues.

The last five spirits are also not really missable. The first one is sitting in front of a furnace directly on your way down. The next one is running around in the corridor further down. The last three spirits are on the "revival" shrine. Also make sure all three are greeting you, then you should get the achievment. :)