When we sweeten we use a gallon jug. We rack about 3/4 of a gallon into the jug then add the simple syrup to the gallon juga few tablespoons at a time. Stir well then taste. Once we find what we like we add the syrup to what is left in the carboy, (for a 6-gallon batch, multiply the # of Tbs by 5) stir, then add back the testing batch and stir some more.