They are quite easy to maintain. Just lay it down on the stone and hone, alternating sides. Both sides have flat honing surfaces, with a hollow grind inbetween the flat surfaces. It therefore has a built in jig. Some prefer doing more strokes on the front side, but I haven't had a problem just alternating.
The classical natural stone for doing kamisori is the Nakayama - either the Asagi or the Iromono (often referred to as the Kiita). The Ozuku Asagi is another very hard stone that works well. The Nakayamas are hard to come by these days, but I did get a couple of them in
They also take a very fine edge using compounds, going all the way up to 0.025 micron Poly. Exceptionally nice shave!