A: For many years there was a heated debate around this topic with manufacturer’s stating flatly the notion their products actually damaged knives was absurd, and many professional chefs claiming not only was it not absurd, it was common for mechanical sharpeners to damage expensive cutlery. So who was right? To a certain extent they both were. The manufacturers were correct in asserting that if you followed the instructions to the letter there was little if any chance your knives would be damaged. However, in reality few people actually followed the instructions to the letter and when they veered from the recommended course the potential was there for damage.

To take off the fine scratches and burrs left by coarser stones, and to polish the surface, you can use stones starting at around 2000 grit. There is theoretically no upper limit, but stones above about 10000 grit achieve practically no measurable improvement in the edge. It is also interesting to note that above 8000 grit, there is no Japanese measurement standard. For stones labelled as having a finer grit, you simply have to take the manufacturer's word for it. 

The stone – With a sharpening stone, the process is essentially the same as with the stick sharpener. The only difference is that you don’t hold the stone, you place it into its own holder (If it comes with one. If it doesn’t you’ll need to improvise) on a flat surface. Push the knife down the stone several times while holding it at a shallow angle and then flip it and pull it toward you several times to get the other side of the blade.
Also natural stones have a random grit size that gives a long lasting edge. Basically the random grits create varying sizes of micro-serration in the blade that wear down at a different rate, therefore longer edge retention. Whether this is true or not we really like natural stone, especially for sharpening tradition single bevel Japanese knives. Use natural stones with water – it’s far cheaper than sake.
However, due to limited natural deposits and extensive quarrying over the centuries, true, high quality, Japanese water stones are now few and far between and are very expensive. Thus, various companies are now producing synthetic Japanese Water Stones which generally have a more consistent composition and grit size than natural stones as well as often begin somewhat harder and thus, lasting a bit longer; not to mention being cheaper to purchase.
Once sufficiently wet, it's time to position the stone on something solid, so it doesn't move about during sharpening. Many come with holders, but you can just place it on a slightly damp tea towel on the table. The stone should be roughly perpendicular to your body, though Warner told me it is sometimes easier to angle it ever so slightly to the right (if you're right handed). 
One of the most well-regarded natural whetstones is the yellow-gray "Belgian Coticule", which has been legendary for the edge it can give to blades since Roman times, and has been quarried for centuries from the Ardennes. The slightly coarser and more plentiful "Belgian Blue" whetstone is found naturally with the yellow coticule in adjacent strata; hence two-sided whetstones are available, with a naturally occurring seam between the yellow and blue layers. These are highly prized for their natural elegance and beauty, and for providing both a fast-cutting surface for establishing a bevel and a finer surface for refining it. This stone is considered one of the finest for sharpening straight razors.[citation needed]
Removing the burr is fairly simple. You'll need a leather strop or block (this sort of thing), which is designed to catch the metal fibres from the knife. You could do it with a fibrous tea towel or some newspaper if you like, but I'd suggest going with leather to begin with. The motion is fairly similar to sharpening. Draw the knife over the leather, going away from the edge at roughly the same angle as when you sharpened. 
at the end, metal is going to vanish. Don’t start with a Dollar Store knife, start with a medium quality 8 inch (203mm) that has not been sharpened beyond the factory before you. You want to set the sharpening stage for success, a cheap knife is hard to sharpen because of the inferior quality of the steel. Now if you are worried about scratching the blade of the knife, you shouldn’t be but if that apprehension is going to distract you, eliminate the fear by taping the blade of the knife with painters tape, just the blade, not the edge.
At age 10, Terada learned the basics of sushi from his father and then went on to attend RKC Chef's School in Kochi, Japan from 1987-1989. He soon earned a nickname for his fast knife, attention to detail, divine presentation and ability to create new dishes and accents based on traditional Japanese cuisine. After graduating RKC Chef School, he was called to serve under Master Chef Kondo at Yuzuan restaurant in Kochi, Japan from 1989-1992. Mr. Kondo is the master of Kansai style cooking, considered to be the high-end of Japanese cuisine. Terada earned the title Master Sushi Chef by becoming the standing head sushi chef & can serve Fugu (Japan Licensed) to the public.
However, because the Belgian Blue stone generally occurs in relatively wide columns with much thinner layers of Vielsalm Coticule on either side adjacent to the slate, the Belgian Blue stone is more plentiful that Coticule and thus, it’s somewhat less expensive. But, it’s also somewhat softer than Coticule and is not divided into different grades as Coticule is. Furthermore, because it is a softer stone than Coticule, it is sold without a substrate layer.