Herb, you may not want to hear this, but normally, when RC modelers do panels lines they start with a fully sheeted and glassed model. None of the usual techniques work on an unsheeted model. Perhaps the most common technique (to simulate edge to edge panels) is to lay down very narrow strips of trim tapes. I think these are available down to 1/64 of an inch. Next, the model is strayed with several coats of primer, until the tape is covered. Then you lightly sand down until the tapes are reveal and then peel them off, which leaves the primer higher than the area underneath the tapes. This technique wouldn't work over "open" structures.

The other technique simulates overlapping panels. And it's essentially the same trick but instead of building up primer on both sides of the strip you only spray on one side so one side ends up higher. This can be feathered down on that side.

One way to simulate panel lines on an ultracoat covered model might with be through a very artistic paint job, where you carefully mask each panel and subtly paint it so that the colors give the impression of discontinuity. This would take considerable airbrushing skills.