It is better to understand the difference in sharpening stone materials before you are going to make any decision. Among the available options in the market today, Waterstone, oilstone and diamond stone are the most common type of sharpening stone. Each of stones comes with advantages and disadvantages. Waterstone and oilstone are available in natural and synthetic models. Synthetic are the most common and easy to find as man makes them. As the use of natural stones (e.g. original Arkansas or Japanese natural whetstones) is has diminished in popularity, they are beginning to rare in the market. Artificial stones have a more consistent particle size and controlled with a tight mechanism in providing high-quality sharpening stone.
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). 
Vielsalm Coticule on the other hand generally occurs in much more narrow layers sandwiched between the slate layer and the Belgian Blue layer and thus, it is both less plentiful and more expensive than Belgian Blue stone. Also, Coticule is divided into different grades and sometimes displays blemishes on the surface due to its proximity to the slate layer. Furthermore, it is somewhat harder than Belgium Blue stone and, due to its brittleness, it is bonded to a substrate layer of hard slate prior to sale to prevent the stone from breaking during use.
Your kitchen knife becomes dull when the metal at the primary edge, the cutting edge becomes fatigued and rolls over to one side or both sides of the blade. This is normal, it should happen regardless of the quality of the steel and what you are using the knife for. The difference will be “when” it gets fatigued, the better the steel the longer the edge will hold out, generally speaking. However, I have noticed something with high quality knives such as a Fujiwara and this may be applicable to you: I have several different brands of knives ranging from mediocre to my one dream knife. Theoretically, the mediocre knives with their mediocre steel should become dull faster under normal use. (I am referring to use at home, not in professional kitchen and not in the hands of someone who cuts lotus blossoms all day long)
Sharp knives make the culinary world go round but finding the best knife sharpener isn’t as simple as walking into the store (do people still walk into stores?) and grabbing the first sharpener that presents itself. There are different types of electric sharpeners, some that are straightforward and some whose sharpening process involves as many as 3 or 4 stages. If you’re looking to keep things simple by using a sharpening stone well, there are 3 different types of them as well – oil, water and diamond – and they each have their pros and cons. So it can be confusing.
Your immediate goal is to raise a burr on the side of knife opposite to the side you are sharpening and depending on the steel, the grit of stone and how you are doing, it will be either a very quick process or it will seem like it takes an eternity. Patience here will reward you, believe me. The sharpening process is incomplete with no burr creation on your first stone. (Yes, it is possible to stop at that magic moment without the burr forming but we are not there yet, we don’t even need to go there, ever, I am just mentioning it so those gifted sharpeners will be happy) . Think of the burr as the debris that is making the knife dull being forced down the blade towards the edge and over to the other side of the by your sharpening prowess. You form the burr, that knife will get sharp, no burr, you just need to look at your work. A Loupe is handy here, an inexpensive magnifying device with a light that allows you to see the edge very well, if you are not forming a burr, you are not reaching the edge. (Having a loupe also makes you look cool and scientific, like a Sharpologist).

The final Chef’s Choice sharpener on our list is the 316 Diamond Sharpener. Like the 15XV the 316 is at its best when used to sharpen Asian-style knives and it does so with unflinching effectiveness and speed. This is a compact, 2-stage electric sharpener that produces the 15 degree edge so favored in Asian cutlery. Ideal for the preparation of sashimi or sushi.
Beginning on the right side of the knife, move from tip to heel and heel to tip, then flip the knife and repeat. For the left side, it’s opposite—start at the top of the stone to reach the heel area completely. So, you will move from heel to tip and then tip to heel. Remember to apply and release pressure as you did earlier, exactly the same as in Step 2, but with light, refining pressure.
In recent years, some whetstone manufacturers have started producing ceramic whetstones made from hard, ceramic, powders that are mixed with Aluminum Oxide and then sintered to form a solid. But, rather than using oil or water to lubricate the whetstone, ceramic whetstones are meant to be used without lubrication and thus, they provide a significant advantage for chefs who need to keep their knives sharp but, who do not have either the room or time for using a bench water stone. Thus, they are commonly available as either bench stones, pocket stones, round rods, or triangular rods.
Not sure why I bought this item and then I received it. It has a bit of a 'cool' factor and is well made. I took the sharp edges of the stone as they were a bit uncomfortable on my chest but have since been wearing it a lot. Used it to put an edge on some workmates knives and to tickle up my own daily use knife. I like it, it is a bit different and useful.
It will be tempting to raise the angle here to get to the edge quickly, that is not the way to go. Re-paint the edge/bevel if necessary and try again. You can flip the knife prior to burr formation and work on the opposite side. Repeatedly feel for the burr with your thumb by running it very gently down the blade and over the edge, if the burr is there it will be very obvious, you need to create the burr along the entire length of the blade. Once you have done that, (you have accomplished what most people will never try) but besides that, you have to do the same to the other side of the blade.
The Whetstone 2-Sided Sharpening Stone is made from professional grade corundum and will sharpen everything from a razor blade to a cleaver and even a machete, should you happen to have a machete lying about that needs sharpening. This is the simplest type of sharpener it’s true but the company have obviously put a great deal of thought into the product.
Selecting the proper coarseness for your sharpening stone is an important first step in sharpening your knife. Not every knife needs to start at the coarsest stone you have, on the other hand a very dull knife can not be sharpened on only your finest stone. Starting with the proper coarseness will ensure that you achieve the edge you need quickly. If your knife is very dull or has a nicked blade, start with your coarsest stone. The coarse stone removes material quickly so a poor edge can be refined quickly. However, the coarse stone must be followed up with your finer stone to refine the edge. If your knife is only slightly dull and just needs a quick touch up, starting at a medium or fine stone can save you time. Starting on a fine stone requires fewer steps but must only be used on an edge requiring little work.
I recommend it as a lightweight alternative to larger stone for smaller knives. Leather necklace is comfortable and seems strong. I conditioned it for suppleness and swim with it on tightened as a choker. Stone is small, dog-tag size. I use it with water. Functional for small folder knives and multi-tools. Not useful for large fixed blades, since you can't make a long stroke. Small to grip. I use double-sided tape on one side to keep it in place on a flat rock. Not sure of grit, seems like around 1000. It took a while, but i got my old boy scout knife sharp.