There is a 4 page article on this in Black and white magazine (I think it's the March issue, but I could be wrong). I think the author is Andrew Saunderson who also did an article in this mag on the new Walker 8x10 camera.
I have only recently started using split grade printing and have found it very helpful with some difficult negatives. As others have said, you don't need it for every neg, but for others you do.
cheers
Mike