The tourists managed just one wicket all day as Smith and Marsh, with a career-best 229 and 181 respectively, shared an unbroken fifth-wicket partnership of 301.
Australia finished the day on 549 for four in reply to England’s 403, leading by 146, and in a strong position to regain the Ashes with two Tests still remaining.
But Farbrace felt England’s bowlers did all they could, telling Sky Sports: “We have had a tough day.
“They played exceptionally well. Smith has played well, as he has done all series.
“You can look back at how your bowlers bowl. We think we have worked really hard as a bowling group and toiled away really well.
“We haven’t got the extra pace that the Australians have got and we don’t have magical spin. We have what we have. We knew that coming into the series.
“We knew there were going to be times where it was going to be tough for our bowlers and today has proved to be one of those days.
“I thought our body language was pretty good. We stuck at it pretty well. I think watching it from side on, we worked hard and got stuck in.”
Australia are now overwhelming favourites to recapture the urn over the next two days.
But Farbrace is confident England can still save the match and keep the series alive.
“Until the Test match finishes you have to believe you can get something from it,” he said.
“We came into this game believing we could get something out of it and keep the series alive going into the next game. There is nothing to suggest that we can’t still do that.
“Yes, it is going to be hard but that is what it is. It is Test cricket, tough cricket, and you have got to get stuck in.”