Sharpen a plastic one, when it gets full of wax, i.e. 3-4 times when scraping a board; just turn the edge of the scraper perpendicular (90 degrees) to the edge of the board and pull. If the edge of your board is relatively sharp it will sharpen the plastic edge of the scraper. But if you want to polish it, use plastic polish.
As for metal....you pull the scraper at an angle greater than 90 degrees...don't push it.
Last edited by wrathfuldeity; 02-19-2013 at 10:37 AM.