The first tip is to get a vinmetrica SO2 meter and then add only enough metabisulphite to reach a 25ppm target. Do not add campden tablets, instead use powdered potassium metabisulphite and weigh dosage to 0.01 gram accuracy.
Along with that it will help running the pH low on your wine 3.2 or 3.3, such that the meta has a higher percent active SO2.
