Swapping buttons on a GameCube controller
Yes, that's the general method. You scratch off the solder mask, then cut the trace in half. Then you solder on a thin wire from one side of one trace to the other side of the other trace. Like an X/criss cross. That's it.

This is commonly done on arcade cabinet projects. Here is a YouTube video of a Xbox 360 controller rewired for southpaw usage. 

The 360 controller is much more complex. The GameCube controller can be rewired with even a beginners soldering skills.