I've done it using solder and a special electronics soldering iron that I have. There is an easier way.
Lay out some large anti-static bags and tape 'em down as a work surface with the mobo laying on it.
Use a flat tipped exacto blade and a magnifier to clean off the enamel on only the trace you want to repair...both sides. Use it as a scraping tool, and not as a chisel. I have the 4" lense from one of those flourescent magnifier lamps.
Now get a trace pen. It's a conductive paint marker with a felt tip that's made to do this...very handy. Just draw a line connecting the two stipped spots. Use a couple of coats to make it good and thick because some traces carry more power than you might think. If the broken trace is all that's stripped, then the pen's mark won't contact the other traces. If you've slipped and striped more than one trace, use some nail polish or model paint to re-cover all but the intended repair victim before using the trace pen. Let the marker dry thouroughly between coats. If it's a large trace (read-heavy power conductor) you can bed a small copper wire in the trace paint to enhance it's power carrying ability. Just lay it in wet paint, let dry and then coat again over it.
When it's thouroughly dry, use some model paint or nail polish over it (NON METALIC variety)
The trace pen is the easiest way to do this repair, especially if it's not out in the open like my repair was. You can get a trace pen at any electronics store, or you may have one from unlocking your t-bird.
Best of luck to ya!