Its funning that this thread has come up, because I have done a lot of research on this and have found 7 DVDs you can purchase and a book by Kosen Judo black belts. I purchased them and I am starting a Kosen judo program at my school.
There are 7 universities in Japan that still teach Kosen judo. They have some great history, I E. Masahiko Kimura. I have also found a school in Utah and he has there curriculum and belting requirements on his web page
What you will discover is that many of the techniques that the Brazilians package and sold as there own where already being done by these guys, hence the old saying nothing new under the sun.
Also a Kosen black belt is about the level of a purple belt in bjj. It takes about 5 years to get it, give or take. They consider the degrees of your black belt as a true testimony of your skill level. Much more reasonable then the 10 years in bjj along with all the $100.00 To $150.00 seminars ( with the same techniques shown over and over) that you have to keep going to if you don?t have a black belt in your area.
Anyway I could go on but I would suggest that you do a search on the internet and you can find out all you want to know. You might want to draw some conclusions for your self about the whole thing. For me, it has shed some light on a lot a things.
Hope this helps.