A scraper is a wedge-shaped tool with a knife blade at each edge that is used to scrape away metal, usually to remove marks incised in the plate. The scraper leaves marks of its own that must then be burnished and polished if the formerly marked plate area is to be made smooth enough not to hold ink.

Artist Judy Pfaff uses a scraper to make marks on the plate.
A burnisher is  bent, rounded tool, not a blade, for making changes in a metal plate after it has been incised. The burnisher, used with oil, smooths out marks after they have been diminished by scraping the metal with a scraper.
Smooth out marks in the plate by using the burnisher.