Okay, two of them dried, so I tried out my paint scheme on them. A road tile, and a city block tile.
Okay, so I'm working with three shades of grey as the main colours. There is just a very slight hint of warmth in the shades, I think - not pure black & white. As I mentioned previously, I went to the local hardware store and got three 'sample' tins of paint mixed up in the three shades, so now when I need a shade of grey, I can use an eye-dropper (available from chemist shops) to put paint out of the tin and into empty miniature paint pots. I found though, that with the amount of painting required to do these boards, I ended up just going straight from the tins.
I undercoat in the darkest grey
For the road surface hold the brush so the flat is horizontal to the road, then make vertical strokes up and down the road. Continue to only put a little paint on the tip of the brush. This will make a slight streaky effect up and down the road. Put more paint on the sides of the road than in the middle of the road.
Now go to the light grey. Repeat the same process - a little paint on the tip of the brush, criss crossing strokes with the flat width of the brush.
On the road, only do the vertical strokes along the sides of the road - don't put light grey up the middle of the road.
Okay, the drain and the manhole.
Brush them criss-cross again, using Mephiston Red or any other darkish red
Medium Grey cross hatching followed by light grey crosshatching
Now, put aside the flat wide brush and get a drybrushing brush. (round end, cut off flat like a stump of bristles)
criss-cross with the drybrush over the concrete - but get none in the indentations between the concrete if you can help it.