Try using auto stripes in yellow. They can be purchased at an auto supply store or online. They come thin enough for good looking taxiway markings. They are also flexible enough to use with any curved taxiway lines. It does take a little practice to make them straight and not tear them. They work well on plastic.
Painting the surface and using pin stripe is the best way if you're not photoshop or illustrator savvy. I might add that applying a clear gel medium over the pin stripe helps to keep them in place since they have a tendency to lift over time.
i know this thread maybe old, but im not sure what colour to do my taxiway. i currently have paper on a baseboard for my airport, but im not sure whether to shade in with a 2b pencil or something else???