Adam Duvall clobbered a first-inning homer off his former teammates, and right fielder Patrick Kivlehan overcame a second-inning error by going 4-for-5 with a homer.
The Reds scored in seven of eight innings Friday and in each of the first five this time. They also tallied in Saturday's seventh inning, giving them runs in 13 of 16 innings this series.
The offense provided Reds starter Amir Garrett (3-2) with an excess of support as he limited the Giants to two runs and five hits in six innings.