paperbackmonk: Thank you very much! The map took maybe five or six months with perhaps around 200 hours. This is partially because I kept changing things, was learning and experimenting with different techniques, and was thinking quite a bit of how to arrange and do things. Now I'd be able to do something similar much faster I believe.

CloudFang: Hi CloudFang, I don't use filters much at all when painting. I don't really use a specific blending tool other than the Photoshop brush. I set the opacity of the brush somewhere between 10% to 100% depending on how strong I want the impact of what I'm doing to be. Most painting is done at maybe 50 to 70% opacity. I pretty much leave the flow at 50% or so and let it be. A major part of the blending process is the colour picking/eye drop tool. I may lay down two strokes at 70% opacity or whatever and eye drop the colour created between them, lower the opacity and then paint out the area between.

As for layers, with this style I tend to use only a few layers. Sometimes the landmasses and the ocean are a single layer but sometimes separated. Both options have pros and cons. The rivers may but the trees definitely will have their own layers on top of that. For painting the land however I do tend to keep things on a single layer if possible. if I create a gap due to moving something with the selection tool I'm likely to fill it in with a layer under the main one and merge it later. If I am trying something out otherwise I will create a layer on top and if I elect to keep it, merge it down into the main one layer.
There are pros and cons to using varying amounts of layers:
1. Fewer layers:
-Simpler to keep track of.
-Smaller file sizes that load and save faster and can be worked on more smoothly.
-Manipulating landmasses in a big way is in some ways easier. You can move land around and the mountains or hills on top come with it.
-Less flexibility with revision (though I find this minor most of the time)

2. More Layers:
-More control and flexibility to refine, but the process is more tedious.
-More to keep track of and the possibility of painting on the wrong layer is larger.
-Larger file sizes, more system resources use to work with the file size.

I will use custom brushes to get textures, usually on oceans or when creating parchment looking areas. I tend to paint directly over earlier sketches and outlines although this is not always the case. When I create landmasses I like to block out the masses with a 100% opacity brush instead of focusing on outlines.

I hope that offers some insights