The England international is showing signs of regaining his best form after seeing his game tweaked since Sinfield replaced sacked boss Brian McDermott.
Ferres was bought as a ball-handling, wide-running second-row from Huddersfield Giants in 2016 but was often given a different remit by McDermott.
“I prided myself on being an 80-minute back-rower and that’s what I’m starting to do now,” he said.
“I’ve got a nice role within the team now. Kev’s let me express myself, play a little bit more and that’s my game; I’m not just an out-and-out forward.
“I like to play and create and hopefully that creeps back into my game.
“I think it’s starting to and others can get some fruition off that. It’s certainly pleasing.
“It’s been nice to have Kev in. He’s looked after me and I’ve been playing 80 minutes now for the last four or five weeks.
“I’ve been enjoying it and it’s still a work in progress but I’m looking forward to just knocking a few games off and then getting a good pre-season under my belt and really have a big year next year.”
Ferres, 32, admits he is playing injury-free for the first time in a couple of years and is thriving in Rhinos’ new-look left-edge.
After Sunday’s 48-32 Qualifiers win at London Broncos, he added: “I’ve got a really good combination going now with Richie Myler moved over to the left.
“I’m getting some really good ball from him and with Joel Moon moved back into the centre he’s just a classy player.
“We’re really causing some problems out there and it’s certainly working for us all.
“It’s nice to start hitting some lines, getting off-loads in again and a bit of the old me back.”
Leeds made it two wins from two outings in the Qualifiers so far as they took a big step towards retaining their Super League safety.
London had won at top-flight Widnes Vikings in their opening game so clearly posed a threat. But Sinfield’s side powered into a 48-10 lead at Ealing by the hour mark to get the job done, even if their Championship hosts did finish strongly.
Asked if the club would look at that opening spell or the latter, Ferres said: “Both. Where we’re going on a bit of a journey with ourselves we need to look at both. We were very good first half. We looked a good side and were quite ruthless and consistent with what we did.
“We backed it up with some good defence. But obviously there was a bit of ‘chalk and cheese’. We knew they’d have a say but, that second half, for where we want to be, it’s not good enough for our standards.”