Hmmm... Looks like the basic search bar just doesn't cut it for finding things these days. I hadn't used it in so long that I hadn't realized just how worthless it was. Right below the search bar is a link that says "Advanced search." Go there, then click on the tab that says "Search single content type." Or just click this: Search Forums - Cartographers' Guild

That search page turns up much better results.

I have a bit more time right now to give more specific advice, but nolgroth already hit most of what I was going to suggest. Allow me to add Jezelf's tutorials: http://www.cartographersguild.com/tu...photoshop.html
I like those a lot for coastlines and rivers.

And speaking of rivers, let's just preemptively recommend this tutorial: http://www.cartographersguild.com/tu...ght-place.html
I'll bet our self-styled "River Police" are going to pay you a visit rather soon, and forewarned is forearmed.