"I've spent the last four or five weeks practising with (England assistant coach) Matthew Maynard and it worked really well because I've got my game more solid again," Trescothick said on Thursday.
The left-hander said although he had scored a double century against South Africa the last time the teams had met - 219 at the Oval in 2003 - he had been concerned about his relatively poor record away from home.
"It's always in the back of my mind: why have I not scored so many runs abroad? It's been going on for quite a long time and I've been trying to assess why. As soon
In 28 Tests in England, Trescothick has scored 2,373 runs at an average of 53.93, with six centuries and 15 fifties. Away from home, the 28-year-old has scored only 1,609 runs in 26 Tests at an average of 32.83, with two centuries, one of them against Bangladesh last season, and nine half-centuries.
Trescothick scored 85 not out in the tour opener against a Nicky Oppenheimer XI on Wednesday.
The Somerset batsman said England were "hoping to dominate the series with South Africa.
He added: "But it's important that we keep people fit so the nucleus of the side that has done so very well the last few months can stay together."
The first of five Tests starts on December 17.
