When you look up one of the web pages for the kesurokai I think there are shots of sharpening these, otherwise you have to get in on the one in Luneburg in July,still some openings I am notified by Hannes, there will be a group coming in from Japan for that week, with their yari ganna in hand.
When I sharpen I'm sharpening both edges on the push stroke and a pivot action for the tip, slip stone for the bevel side. If it's correct or not I don't know, it's a good question.