Originally Posted by noseoil
The staining action on your film continues after fixing well into the wash process. If your fix is an alkaline base then you will get good wash stain -- TF4 fits this well. If it is not, i.e. Kodak's Rapid fix, put the film back into the spent pyro developer (alkaline) for a couple of minutes just before your wash.
This second dunk into the developer will just adjust your film emulsion towards the alkaline side of things so you get maximum staining effect during the wash.