I used Future/Klear and water in a roughly 2:1 mix, and added in peat brown and black - also at about 2:1 - topping up with Klear/Water in the same ratios until the mix looked good to the eye.
Here it is slapped on a Xyston Theban. Figure on the left was undercoated gray with white drybrushed over that; figure on the right shows how it looks after the wash and before any further highlighting has been done.
It's a little bit grainy on close inspection, but a highlight and varnish should sort that out, I'd think.
Not too bad, but I might try to go thinner to see if I can keep the need for highlighting to a minimum, and in future I'll use more Future and less water to see if that will reduce the graininess.