The 24-year-old moved onto 5-0 on the undercard of Jack Massey's triumph over Vaclav Pejsar when making light work of Czech fighter Daniel Bazo.
Farnhill, who floored Bazo with a right hand in the second round, had been so relentless that his opponent retired on his stool just a third of the way in.
Manager Kevin Maree said: "You've got to be careful what you do with Reece because you can almost fast-track him too much. We bought a foreigner over who we were told was very durable, but he's just head and shoulders above these guys.
"He absolutely blitzed him. You could see after the first 30 seconds that this guy's whole world fell apart. He came in very confident; we spoke to him at the weigh-in and he said he was looking for the win. I had a wry smile on my face and thought 'you have no idea what you're getting yourself into'."
Maree added: "You could tell straight away that he didn't want to be in there. Reece hurt him, he's an amazing finisher and if he smells that blood he's like a shark, he'll just go after you. He was relentless again.
"Reece is incredibly exciting and it was good to have him on that bill with some top prospects because he's in that mix. He's one of the top prospects in the country. He didn't break a sweat, he's just an absolute assassin."
Meanwhile, former Commonwealth champion Luke Blackledge claimed his first victory in three years when out-pointing unbeaten prospect Wycombe King.
The 31-year-old, who challenged Callum Smith for the British super-middleweight title back in 2016, ended a run of six defeats on the spin when having his hand raised at the Bolton Whites Hotel.
Referee Steve Gray scored the contest 39-38 in Blackledge's favour, which brought up his 27th career win as a professional, and his first since narrowly out-scoring Darryl Sharp in a six-rounder at the same venue.
Maree said: "He's back! He had a fantastic win on Saturday. It wasn't a 'shock', he's in a different stage of his career now, so he won't be in any of these big, hard, long fights anymore.
"Training camps like that are just too much punishment for Luke so I had an agreement with him that if he wants to carry on boxing it'll fit in with his life and there are various stipulations in play.
"He'll go in now as a test for these younger lads and if they're good enough they'll get past Luke because he's not where he was and if not, he'll teach them a few things in the ring.
"Wycombe King fell short, but he learned a lot from it. Luke will do that to these young prospects. It's great for them because they'll learn a valuable lesson: win, lose or draw against Luke.
"He did really well. That was the perfect job for Luke, it was a very competitive fight, he just 'old-manned' him really, and used his experience, got his way through the fight and took it on points. Luke will move on now after four competitive rounds."