Separately, I've found that there are many guides written about how to become shodan, but I've only seen a few written about going from shodan to high dan. I was able to dig up one of them.
https://forums.online-go.com/t/repost-to-become-a-master-of-go-is-not-easy-but-to-become-an-amateur-5d-or-6d-is-not-hard/789 -- this is where I got the 95% number from.
Quote:
You must choose a proper book for you, don’t choose a very very hard book, if you only can resolve 10% to 20% problems, just abandon it. You should choose a book which you can resolve 60% to 80% problems, do it repeatly until you can easily resolve (clear every variations) more than 95% problems, then you should change a book.
Moving on when one gets to about 65% right in a book seems like a good idea (like Bill suggested), but if one does not properly track one's progress until getting 95% right while working through a new book, it seems likely to lose the edge that comes with being extremely disciplined and accurate with your problem solving (in game or out).
To be clear, by move on I do not mean changing books. I mean using a new source for new problems that are a bit harder. (That could be within the same book, such as Maeda's tsumego series.) Keep on reviewing problems you have missed until you get them 100% right, and then review them some more (overlearn them).