They recorded a six-wicket win after bowling out the one-time champions for a mere 91.
Harrison said: "Barry Frankland stood down ten days ago and Matthew Lumb had it for one game before I was appointed and the lads have responded in a positive way."
The result ended a run of three defeats in completed matches and Harrison added: "We can only take positives out of this game.
"The lads have played immensely well and to bowl out Congs on a track as good as that is highly impressive."
It was certainly an excellent performance because the Red Lane pitch is regarded as one of the best batting strips in the Bradford League.
But the Farsley bowlers – notably South African Graham Hume with 5-34 in his 15 overs and with Chris Henry 4-21 in seven overs supported by the other wicket taker Neil Laidlaw – managed to swing the ball with devastating effect.
It was the third five-wicket haul for 23-year-old Hume, who plays first-class cricket for Natal in South Africa and has spent the last two summers playing for Cleethorpes in the Yorkshire League.
Harrison said: "Our bowlers bowled line and length and the ball swung.
"I lost the toss and they decided to bat but I was going to bowl anyway. I thought the ball was going to swing and Chris Henry and Graham Hume can make it swing.
Cong had no answer to Farsley's pace attack, losing wickets at regular intervals with no one able to stem the tide.
Only three batsmen reached double figures as they were bowled out in 29 overs, with wicketkeeper Matthew Green taking five catches which told the story of a swinging ball.
Farsley lost four wickets in reaching their modest target in 23.5 overs to give Congs two bowling points but the result was never in doubt and the match finished at 5.25pm, having lasted a mere 52.5 overs.
Harrison said: "This is a fresh start for the club and can only augur well for the rest of the season.
"I captained Burley-in-Wharfedale to success in the Aire-Wharfe League in 2010 and 2011. I was mooted to take over next season but the club have fast-tracked that.
"We want to be challenging in the right area of the table and play a good brand of cricket."
Congs won their first league match of the season, beating Bradford & Bingley by 88 runs, the previous week but were unable to build on that success.
Disappointed captain Gareth Phillips said: "Farsley bowled well, especially their overseas player.
"We gave wickets away at key times and there were more poor umpires' decisions. Nothing goes for you when you are bottom but you should not be getting bowled out for 91.
"We have two target matches coming up against Morley and East Bierley in the next fortnight. We have to get points from these two games.