The striker, who netted 44 goals for Gers in just over two seasons, played 90 minutes in the 1-0 defeat for his Derby side at Ibrox, as Nikola Katic grabbed the only goal of the game.
Speaking to RangersTV, Waghorn said: “It was nice to be back, though it was a bit surreal playing on the opposite side. It was good to see some familiar faces and for us as a team it was a good challenge, and I thought at times we were solid, but a little bit of quality at times caused us some issues.
The Rams kick-off their Championship season away to Huddersfield Town next Monday, with Waghorn believing them to be in a good place ahead of that.
He continued: “We have had a bit of a different pre-season in terms of traveling and some of the games being called off because of weather conditions, but the training has been intense and has been good.
“The 90 minutes today was important for us going into next Monday and it has got us up to speed where we want to be.
“The way he talks on the training pitch is brilliant – it’s really informative and us as players can only learn from that and benefit from it.
“It’s up to us on a matchday to put that into practice in a real-life situation, and hopefully we can go and start well this season.”
Waghorn was also hugely impressed with Gers and the showing they put up, adding: “The boys are in a great place and it shows with the way they played against us with the difference in the transition between defending and attacking and the speed at which they break.
“There are positive signs and hopefully they can go on and have a positive season.”