"It's nice to know that I'm going to be in there and my role has changed a little bit," Posey said. "I'm counted on a little bit more now."
Posey drove in six runs, going 4 for 4 and scoring three times. He capped a seven-run fourth inning with his slam.
"Everywhere he's gone, he's hit," Giants manager Bruce Bochy said. "It's just a matter of him getting at-bats up here on a consistent basis I think, and that's what's happening."
Lincecum (9-4) needed only a fraction of the support. The two-time reigning NL Cy Young Award winner scattered four hits in seven innings.
"I feel like I'm gaining a little bit more strength here coming into the All-Star break," the right-hander said. "My pitches are doing what I want them to, so I was able to get on track tonight. It was good."
Lincecum had lost his previous two starts. He avoided dropping three starts in a row for the first time in his four-year career.
"That's why he's won two Cy Youngs. This kid, he's special and you're going to have bumps in the road and it's something that he's had to overcome," Bochy said. "Timmy looks, now, like he's on a mission to get back on track."
The Giants are back on track, too, and are a win away from completing a four-game sweep on Thursday after coming into this series as losers of eight of nine. San Francisco has outscored the Brewers 27-4 in the first three games and every player in its starting lineup had a hit Wednesday night.
It was Milwaukee's fourth straight loss at a time when the club is trying to decide its role in the trade market.
"It's a test of your manhood. You can shrivel up and die, or you can come out tomorrow and give it all you got. Who knows?" Brewers third baseman Casey McGehee said. "We might lose 15-1 again tomorrow. We are not going to go out there defeated before we go out there."
Lincecum, the first Giants pitcher with three straight All-Star selections since Juan Marichal, had lost consecutive starts five times in his career. Staked a 4-0 lead when he took the mound, he stayed aggressive and kept the Brewers guessing for his 49th career win.
"People say his velocity is down, whatever, but look at his numbers. He's going to the All-Star Game," McGehee said. "He's not just some geek off the street out there throwing. We knew we had our work cut out for us."
Torres led off the game with a homer and Huff made it 2-0 against Chris Narveson (7-6) with a second-deck shot. Posey's two-run homer made it 4-0.
Posey moved from his usual catcher's spot to first base a day after being hit by a pitch on the left knee. He has 13 hits in his last 25 at-bats, and saved his biggest shot for the fourth.
Narveson's throwing error on a bunt by Lincecum helped the Giants loaded the bases and Freddy Sanchez tripled to make it 7-1. Narveson walked two more to load the bases again and Posey homered off reliever Chris Capuano.
Posey became the first Giants hitter with six RBIs since Barry Bonds did it in 2007.
"It doesn't feel real. Probably the best hitter of all time and to just even be mentioned in the same [sentence] is surreal," said Posey, who had to give up a bat and a signed ball to get the grand slam ball back from a fan.
Edgar Renteria, who'd been hitless in 16 at-bats before two fourth-inning singles, drove in a run in the sixth. Torres doubled in two more in the inning to make it 15-1 as the Giants finished piling on the runs.
"It's fun to watch our lineup blow up like it did tonight," Lincecum said.
Rickie Weeks homered off Lincecum in third. ... The Brewers have one hit in their last 27 at-bats with runners in scoring position. ... According to STATS, the Giants last hit three homers in the first inning on Aug. 22, 1999, also against the Brewers. ... The Brewers announced they'll replace Miller Park's scoreboard next season with the third-largest display in baseball behind ones in Phoenix and Kansas City.