Trumbull snapped a frustrating run when he began well under jockey Tommy Berry and then raced away in the straight to win the Listed Civic Stakes (1300m) at Rosehill on June 27, his first black-type victory and sixth win from 18 career starts.
The four-year-old gelding is the early favourite to add another Listed race win in Saturday's Winter Stakes (1400m).
"I couldn't be any happier with him," Waugh said.
"He is coping really well. He has had eight starts this preparation but his work is brilliant and he's holding his condition very well, so he's a very happy horse."
In his previous four starts before winning the Civic Stakes, Trumbull had not helped his chances on each occasion when he jumped slowly from the barriers before running home strongly, registering two second placings, a third and a fourth during that period.
"Naturally you don't like to see horses missing the start like that for no apparent reason," Waugh said.
"We gave him some barrier practice at home and he was jumping fine.
"Tommy got him out very well last start so hopefully he can do the same again on Saturday.
"It was a well-deserved win last start after a number of close seconds and thirds.
"He pulled up really bright and well after that and his work has been as good as ever."
Waugh considered Wednesday's Listed Ramornie Handicap (1200m) at Grafton for Trumbull after his last start but decided the Winter Stakes was the right way to go.
"I just thought the 1400 metres would suit him better at this stage," the trainer said.
Waugh said Trumbull could have a freshen up after Saturday and be given his chance in some spring races.
"He's a very good horse and he has run great sectionals this preparation," Waugh said.
"He most probably should have won a few more races than what he has."