I’m trying this material for an asphalt road and what I’ve done so far looks fairly good for an amature, 'cept I got it a little too thin in places. Can you go back and had more and if so, do you wait for that first to dry, then sand it before adding the next coat?
Jarrell
Sure, you can add another layer with no problem. It’s just like putting on the first layer, although you might want to start with the putty mixed a bit thinner to allow you to “feather” it at the edges.
Trick 1: Don’t mix too much at once. I use a big yogurt container, and mix no more than about a third of the container (mixed putty) at a time.
Trick 2: To that, I add about a tablespoon of vinegar. This slows the setting down and lets me work with it longer.
Trick 3: When I start working, which is right after I add the vinegar, I have a small yogurt container half-full of water and a 1-inch foam brush nearby. (My wife likes yogurt.) After I spread on the putty as well as I can with a putty knife, I start smoothing it with the wet foam brush, adding more water as necessary. As long as you keep adding water, you can probably keep smoothing for about 20 minutes. Eventually it will set hard, but this technique lets you get a pretty good surface. If the water starts to get cloudy, change it and rinse the brush. You can keep the brush clean enough to use it again if you do this.
After it sets up (an hour or two) then you can sand it. If you did the water brush thing well, a light coat is all you’ll need.
The Durhams Water Putty and the foam brush are both suggestions from Bob Grech, by the way.
Great! Thanks Mr B. I was worried that I was going to have to break the road up and start over again. I like this Durham’s technique and maybe after I gain some experience with it I can turn out some decent roads. Got some parking lots and other stuff in mind too. 
Thanks alot of the advice and tips!
Jarrell