yeah, In my opinion he's one of the best in rpg-cartographers-land, love his work! As for my personal analysis... don't think he uses many brushes (except the triangles to mark hills) and its mostly handpainted. What makes it so good for me is the consistency and color-scheme:
- 'terrain symbols' are very unique to his style and drawn very consistent yet none is repeated exactly the same
- the color-scheme itself is great (very subtle water-color effect, with many shades of only a few main colors, saturation is low and no huge value-differences, e.g. the hills have barely any shades)
- Also coloring is very consistent (all terrrain is colored exactly the same and only a few colors are used as base colors, incl. the labels and linework, which also have coloring)...
- for the texture i think it's just the parchment popping through from the back giving it a great final touch...
well, just what I see, maybe we are lucky enough for Mike to drop in and give us some tips cheers, DJ