I'm not able to answer this, but I have used two-bath fixing since reading this post from Michael Gudzinowicz at the once wonderful rec.photo.darkroom, now a mess due to spam etc.



https://groups.google.com/forum/?hl=en&fromgroups=#!searchin/rec.photo.darkroom/gudzinowicz$20fixer$20complexes/rec.photo.darkroom/m6T6NzxwPQo/yWteXry7PnUJ



If the link doesn't work try going to

http://groups.google.com.au/groups?h...photo.darkroom

and search for "gudzinowicz fixer complex" and you should find it.

He doesn't address using sulphite as an antidote for overused fixer, but he does describe the process of fixing in such a way that I was frightened to ever be tempted to use overworked fixer (for FB paper, anyway).