The kind of sharpening that is being refereed to is more for a cabinet scraper which is a thicker hardened piece of steel with a flat corner edge that is sharp. You burnish the edge with a round steel (a screwdriver shaft will do_) and push the corner away forming a bit of a lip that is sharper than it was before. However... for what you want, you can use any of those cheap scrapers with the 4-way replaceable blades. To sharpen it, just file it towards the cutting edge and it will work fine.

Cheap scraper like this will work fine.

http://www.reddevil.com/index.php?main_page=product_info&cPath=60_75_76&products_id=839&zenid=mv0paifvh01k2j8hnebdglvou6

I have a Sandivk tungston replaceable blade one and it stays sharp about 800 times longer than regular steel.

like this

http://www.woodworkingshop.com/cgi-bin/0B14D5CF/mac/additmdtl.mac/showItemDetail?loadItem=SK66500

I do like my cabinet scraper blades the best. I have some oldies that are thick and very high quality steel.