Samura Whetstone #1000/#3000
The whetstone with grain sizes of 1000 and 3000 grit is the most versatile one. It is exactly the grain size that allows to effectively tackle the two tasks at once: the rough sharpening (remove microflaws and wear scars) and the finish sharpening (bring the blade and the cutting edge to the flawless condition).
Even a novice can easily use Japanese Samura whetstones. You can sharpen even high-quality knives with highly dense steel in your kitchen.