Using the Walthers Cornerstone Street System for the "town" on our layout. After powering through the tedium of adding the tiny "curb" sections as well as the sidewalks to the streets, I like the look... but not thrilled about leaving the colored plastic bare. I think painting it would help. Probably going the brush route on this, rather than spray (not 100% certain on that but...)
I might go broke using the tiny 1oz (?) bottles from the hobby shop; are there bigger bottles, maybe 1/2-pint or at least a few ounces, but where? And what kind? And what colors look best for the concrete and asphalt?
Craft paints, available in the Walmart craft department, or craft stores, like Michaels, are a lot cheaper than model paints. They come in plastic bottles about twice the size of my Tamiya model paints and are a fraction of the price.
Craft paints are water-base, flat colors, and quite thick. They give excellent coverage in one coat, when brushed on. They can be thinned with water for airbrushing, but are sometimes temperamental when sprayed, and don't cover as well when thinned. I use a mix of light gray, and yellow, for concrete. Eyeball mix, trial and error, I have never written down a recipe for it. There is much more gray than yellow, so you might try 3 parts gray to 1 part yellow to start.
Asphalt starts out very black and semi-glossy when it's brand new. It quickly fades to a medium gray color after being run over by enough vehicles. Weather affects it too, much more than concrete, though concrete weathers too, just not as much or as quickly, as asphalt. Strong sunlight accelerates the fading of asphalt from solid black, to dark gray, to light gray. Winter weather creates the well-known motorist's delight, potholes! You might want to add a few. In larger scales, an asphalt road can be simulated with wet-or-dry sandpaper, to show the texture of the real stuff.
The "old and weathered" asphalt road in the photo below was made with wood filler, painted with craft paint.
good luck, have fun!
Traction Fan :smilie_daumenpos: