Hi everyone. I've been working on Wilbur in order to make a terrain for a story I'm developing. I already have a height map and a shaded relief I plan on using for various maps. Yesterday I was researching on some relief shading techniques and I stumbled upon this one, maybe you're familiar with it:

http://www.reliefshading.com/colours/grey/

At first, it seemed easy to implement it in Photoshop, using an image of mine I've attached below. However, I've tried to do it on my own for days and it's no use. What is the best workflow for this type of techniques? Do you have any helpful documents? Thank you in advance, I'm going crazy with this!

If you need more information I haven't said feel free to ask.

Click image for larger version. 

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