See: her tutorials. tutorial one and tutorial two
Here my first tries at this "new-to-me" art form. The second two are on Renaissance tiles. The first on a white sketch pad.
The one above was done with Inktense watercolor pencils, Sakura micron 01, white gel pen, and graphite.
The two below were done with Prismacolor watercolor pencils, black micron, and
Signo Uni-bal UM 153 gel pen, and graphite.