The original post sounds like you want to apply the reducer to prints, as is frequently done for local control. The version of Farmer's reducer usually used for prints is a cutting formula, rather than proportional. As to whether the ammonium thiosulfate - citric acid brew would work, try it and find out. Both ingredients are cheap, and an experiment is a good way to find out if it works for your situation. If it doesn't, you haven't lost much. Fog reduction, with some contrast increase, in prints (usually due to aging paper) is usually best handled by adding benzotriazole or a similar anti-foggant to the developer.