Since a few people have asked for a step-by-step guide to do this, I thought I would share this with everyone.
It's alot of "measure by eyesight" though, so it might end up a patch different when you do it - But it should be almost the same.
1 x 25 cl Black acrylic paint (Bought in a hobby store)
1 x 25 cl White acrylic paint (Bought in a hobby store)
1 x 25 cl Dark brown (burned umber) acrylic paint (Bought in a hobby store)
1 x Light brown (either buy this along the others or use the one in the scenery pack from GW. I used the one in the scenery pack)
2 x Black primer (GW/Armypainter/equvalent)
1 x Sealer spray (Armypainter matt)
1 x large brush (roughly 10 cms in width)
1 x medium brush (roughly 6-7 cms in width)
1 x patience
1) Prime the board in the black primers. You should be able to prime roughly 3 squares per primer bought in the standard size, including the sides of each square. (Good tip; Don't try to paint the raw surface with standard acrylic paint, as it will slide off and not cover. It's a mess)
2) Once they are all primed, put the board down all together. Now the mixing begins.
3) Start off with a very dark grey - I believe I did something along the lines of 1/5 white/black. Drybrush the entire board with the large brush. Now you have a very dark board, with a few texture marks.
4) Add a bit more white to the solution, so you have a 2/5 white/black mix. Now you drybrush, using the same large brush, the edges of the mountains, the cracks on the ground and the stone paths. Drybrush a large area around them, and don't be stingy. If done right, you will notice that it doesn't spring out too much, but you got some attention on the areas from a few feet away.
Important tip; Never go to the edge of a square with this grey or any of the lighter ones. The goal is to have all edges the dark grey, as then you can put the board together in any way you wish, without having some funky transitions between colors. The only exceptions to this are the mountains, which is the reason why you put down the board before you start painting.
5) Repeat step 4, 2 more times, adding 1/5 white more to the solution, and covering a smaller and smaller area on the highlighted parts. You should end up with a near 4/5 white/black mix, making it quite light.
6) Final grey step, add 2/5 white, so you end up at a 6/5 white/dark ratio. Take the medium brush and drybrush the edges very (!) lightly with extremely little paint on your brush. This will give the grey areas on the board the final sunlight touch.
7) Now, unto the brown parts. Don't worry, this one is quite easy compared to the grey.
8) Take the dark brown, and depending on the color and darkness of it, add a little black. Not too much though.
You will notice, before you begin drybrushing with the large brush, that if you step away a few feet from the table now, there are large spots where only the very first dark grey are present. The board probably looks a little... blochy by now. See where there are large dark grey spots; These are the places where you will place your dark brown.
Drybrush large patches of the dark brown, where they will fit. Once again, be carefull that you don't hit the edge of the board. Stretch them out a bit, not making them entirely square or round, but rather likes streaks.
If you're terrified of this stage, look at my board for inspiration as to where to place these spots.
7) Once this is done, mix the lighter brown into the dark. go for a 50/50 mix, so you get a much more leathery look from the brown. Drybrush the large spots in the middle, covering roughly half of the spot from the middle and out.
8) Let the paint dry, while you take a smoke/eat/whatever
9) Seal the board with the matt sealer and enjoy your new gaming board
I would love to see everyone elses boards, if nothing else, then for inspiration.