Sorry, I think my post was somewhat misunderstanding. The pic above is from RobA's tutorial. That's how it's supposed to look after following the instructions that I quoted above.
My problem is, that I added the mountain mask to the mountain colour layer, but the other layers (like the grass, dirt, sea and so on) don't show up! It still looks like in Attachement 1488!
Do I have to rearrange the layers in some way?
Edit:
Now I'm starting to blieve that it might have something to do with this section:
In the PDF, Rob wrote, that you should not just add a new layer, but a new image, as I understood it. The screenshot indicates this, as the file is labeled "1 layer" (and not 19 or something, like in the other).
He then further instructs to "just drop it onto the real map file and it will shop up a new layer". What is this "real map file"? Is it the one that can be found in the journal?! And why did he mention this in the PDF and not in his original post? This indicates that you just add it as a new layer to all the others.
As you can see, I'm starting to get confused...