I've been using photoshop since at least version 5, and I didn't know how to do this. Just because it's never really come up. Given a bit of time I could probably have come up with the solution, but that's just because I've been at it for a long time.

Now this isn't meant as any kind of a flame, either, but for a newbie tutorials are key to learning an app as deep and complex as photoshop. They allow a new user to get something useful done with the app, which promotes further use and experience rather than giving up in frustration. Properly written, a tutorial can be used to demonstrate what those basic principles mean. This is especially important in a fairly uncommon niche like cartography and terrain-building. There are a lot of questions to ask that aren't answered in a standard, "Making your Digital Photos Prettier with Photoshop," book.

That said, it's a really good idea to practice with those cookbook recipes, modifying them, seeing the results, and trying to understand the principles behind them. Think a lot about how you can adapt the various tools used in the recipe for other tasks. For instance, with the technique Ascension describes, you are creating paths, stroking paths and manipulating brush settings. There's a lot of power there if you learn it well and adapt it.