Not to knock Ployglot, but I regularly do this, and add maybe 1 gram of sodium carbonate per liter of working solution to regain the energy. My extensive experimentation states plainly that you do not 'need' 250 ml of STOCK per 36 exp roll of 35mm film (or one 120 roll). You will be surprised with the negative quality using D-76 1 + 3 (but no further dilution, please) with the carbonate. That's only 60 ml of 'stock' per 36 exp roll, heresy to some but my experimentation proves the validity.
Decide upon a regular dev time by testing with an exposed couple of inches of film and agitate for the same time as normal. To really gain precision with this use only a pro-rated amount of working solution for the couple inches of film, ie, if you use 250 ml per 36 exp roll then use only 25 ml per one tenth the amount of film. Use a plastic film container for the 'tank' and do this in total darkness. (These plastic containers hold a max of about 30 ml so this is ideal for a couple of frames which will fit in without overlapping.) Line the film against the container wall, emulsion side out, naturally. - David Lyga