As far as i know any of the common edges can be made with nothing but a whetstone. Some need more complicated motions than others, but if you learned the motion and can recognize which edge a given item has, you can sharpen it. This is something you should be able to do with relatively low skill, compared to the skill cap. But using the wrong technique on an edge is still a danger early on.
But restoring a edge that's been damaged is something else. You lost material in that case, at least in something like 90% of the time. It is not just making that section sharp again, but you need to sharpen it in such a way that.. I don't really have the word in english. You have to keep the shape of the edge intact. No places where the edge moves back from the cutting line, no wavy line along the edge. The techniques to do that are not noticeably harder than just sharpening, they are mostly the same actually. But the knowledge which to use and on how much of a length of the edge to apply them, and when to stop, judging when, or even if, you have achieved a proper flow of the edge again, is very difficult.
And that last bit, while wholly fitting for tools, is not as rigid for weapons. IIRC the vaunted Katana needs quite some maintenance and a normal battle of its time could routinely destroy more swords than it killed fighters. Nonetheless it is considered a good, useful weapon.