The process was very simple, first I located the markings with white or yellow colored pencils. Just a couple of small marks at the beginning and end of each roadway marking. Then I lined up a straight-edge with the marks, and simply draw on the marking with an acrylic paint marker. It took about 35 minutes to do all 36 feet of roadway. You can see the result in the following photos:
Despite the rough surface of the pavement, the markings came out very bold without much effort.
The Elmers Painter paint markers and the colored pencils used are pictured below:
The markers are available from Dick Blick art supplies in the US:
I probably wouldn't have thought to mention these, but happened to come across another gamer's post this weekend talking about the work invested in masking his roadways to locate the painted markings.
In my case, I am creating post-apoc terrain, so want the markings to be end up very faded and sometimes totally obscured. Had this been new or maintained roadway, the markings would have been applied to a smoother surface, and would have been even cleaner and more distinct. After applying the markings, I then began to apply washes and brybrush to "age" the markings. The work isn't done, but the photos below show the beginnings of the process.
A single yellow and single white marker were more than enough to complete my terrain, and probably could have done twice as much. Anyway, just thought that I'd mention them, as they were easy to use and took about a quarter of the time that I had expected.