Hi Tom -
The "Master Paint Striper" looks like it might be the ideal tool. I recognize that gadget from about 40 years ago, but I had forgotten all about it. A double 1/32" line is what I'm looking for.
Over the weekend, I found a forum where the Grafstick tape was recommended for road stripes, so I ordered yellow and white tape in several widths. From another company, I ordered some Decocolor fine-point paint pens, which one review said are superior to the Elmer's pens (more opaque / better coverage).
My final weekend purchase was a 40" flexible ruler. Theoretically, I should be able to bend it to the contour of the roadway, run a paint pen along the ruler to paint the first stripe, then shift the position of the ruler slightly and paint the second, parallel stripe.
Now I think that the combination of the flexible ruler and the "Master Paint Striper" might be the best solution yet. At this rate, I will soon have more dollars invested in highway painting materials than new locomotive would cost!
Live and learn!
- Jeff