The forwards struck either side of half time to ensure Conor Whittle's rocket strike was no more than a consolation for the hosts as Nicky Butt took charge of the young side.
Wilson opened his account for the campaign with a sweet finish after his initial attempt by keeper Chip Sanders while Barmby's effort followed a neat dribble past a couple of defenders. Whittle blasted a 30-yarder past Jonny Sutherland but the visitors were good value for the win.
In front of 2,830 fans, the Reds started the game brighter with Andreas Pereira looking most likely to cause problems. Tom Lawrence could have opened the scoring minutes after kick-off when cutting in from the left but Waterford defender David Breen made an important block.
Pereira continued to trouble Waterford and he forced keeper Sanders into a great save after 13 minutes, dancing his way past the challenges of three Waterford players before unleashing a strike towards goal. Sanders was alert though, and pushed the ball to his left away from the goal.
Ben Ryan almost gave the home side the lead five minutes later. Donald Love fouled Conor Coad on the edge of the penalty area but Ryan’s free kick grazed the top of the bar on its way over. United went down the other end almost instantaneously and struck the bar themselves. Wilson let fly from 25 yards but saw his effort strike the bar, before seeing his follow-up saved by keeper Sanders.
United deservedly notched the opening goal when Wilson finally got the better of Sanders after seeing his initial effort saved, he made no mistake with his second attempt; curling the ball