Allan Johnston made a winning start as Dunfermline manager as his side cruised past Arbroath 4-1 at Gayfield Park in the Petrofac Training Cup first round.Johnston, who replaced John Potter, saw Faissal El Bakhtaoui fire a shot into the bottom corner from 25 yards in the ninth minute.Michael Moffat doubled the lead when he tucked home from inside the six-yard box after Ryan Williamson's cut-back in the 20th minute.El Bakhtaoui claimed his second eight minutes later, heading in a cross from Michael Paton from close range following a fine move.Paton and Callum Fordyce were denied by the woodwork as the Pars dominated the first half, with substitute Ryan Wallace finally adding a fourth with a 20-yard effort in the 62nd minute.Martin Grehan, another sub, pulled a goal back for Arbroath with 18 minutes remaining after the visitors failed to clear a corner.