Australia spinner Nathan Lyon took four for 42 as England limped to 238 for nine on day one, albeit on a ground where low first-innings scores have been typical this summer.
Trott, who put on 73 for the second wicket with captain Alastair Cook (51), told Sky Sports Ashes: "It was difficult, quite hard to score, but from 100 for one we'd be upset at the position we find ourselves in at the close of play.
"But we've got 240 on the board and hopefully we can scrape a few more tomorrow. No one's really sure what a good score is.
"Australia bowled well, credit where it's due, and hopefully we can create the same pressure tomorrow [Saturday]."
Lyon ran through England's middle order, removing Trott, Kevin Pietersen, Ian Bell and Jonny Bairstow, and said: "It was good fun out there, I'm pretty happy with the way I bowled personally.
"I'm happy with the way it came out and happy to build some pressure from one end."
Australia trail 2-0 in the series, meaning England have retained the urn with two Tests to spare after rain denied Australia victory from a dominant performance at Old Trafford last week, but the tourists drew encouragement from that game.
Lyon said: "We spoke about how well we went in Manchester, unfortunately the weather went against us but it was important to continue today [Friday] with the same momentum."