As a linear artist, I have an on-going search for methods to enrich and customise the line. Sgraffito is one of these methods and I use it in two ways:-
Painterly sgraffito: Scraping through watercolour over an oil pastel surface;
Graphic sgraffito: Scraping through oil pastel over a surface covered with watercolour.
(There is a third method, derived from the work of Paul Klee. A line is drawn on the back of paper covered with oil pastel, which has been placed on top of another piece of paper covered with oil pastel on top of watercolour. This produces a highly exotic line.)