The tournament favourites began their campaign with a hard-fought 28-20 win over England in Cardiff on October 26.
However, they won their next four fixtures by massive margins, scoring 210 points and conceding just two.
"I think our preparation has been right," Smith told Sky Sports News. "We had a tough game early and obviously the last four weeks have been a little bit more cruisier for us.
"But we've worked hard to get those victories and to put those points on the board, so I can't see anything wrong with our preparation.
"We are feeling very confident about the game and the plan we have for this match."
Today's game at Old Trafford will see Australia make their 13th consecutive World Cup final appearance.