Cabinet scrapers are great tools, too bad people seem to struggle with sharpening. First you need a good one, Sanvik? Put it in a vice with soft jaws (aluminum angle pc.)Take a sharp fine file and make a square edge. If you feel a bur, it is best to knock that off with a fine stone, flat to the face of the scraper. Take the scraper in one hand and with a smooth screw driver shaft, slide along the edge at about 5 to 10 degree angle with just slight pressure. Don't over do it or the edge will turn too far. One or two light passes per edge. Test on your thumb nail. Should make a nice curl. To use, most people will tilt the blade over too far and pull the edge off. You want to tilt the blade just slightly more than the angle you burnished to. Put a very slight bow in the blade with your thumbs. You can either push or pull. If you did it correctly you will get wide rolling curls that you can see through. If there are planer ripples tilt the blade at an angle to them.
All the fooling around to hone an edge is only worth it if you are trying to smooth a finish. IE take the orange peel out.
You can resharpen the edge several times by just laying the blade flat and burnishing the edge away from the edge. Then do the edge burnish again. Each time you do this it lasts less time. So, 3 times +_? Then it is back to the file.
Most common errors: poor file job, file should be sharp & almost parallel with the blade. Before you burnish, the edge has to be smooth and nearly a perfect 90 degrees. Most people put too much pressure and angle on when burnishing. That will roll the edge too much and make it weak along with requiring you to tilt the edge into the work at too much of an angle. Tilting the blade too much and putting too much curve into it while scraping. Too much angle ruins the hook. Too much curve makes hollow cuts and doesn't take advantage of the flattening capabilities of the blade. Less is more!