The Scot handed returning loanee Joe Mason a second debut alongside in-form Lukas Jutkiewicz and was repaid with a goal from each in a sizzling first-half display.
Despite being a side without a Championship win since Boxing Day and only two on home turf all season, the Whites were in full flow from the off – a diamond of four behind the front two working wonders.
Straight away the strike duo linked up well and on 10 minutes Mason should have opened his account when played in by a lovely Mark Davies reverse pass but his effort was saved by Watford stopper Manuel Almunia.
His opposite number Adam Bogdan kept the scores level with an even better stop at the other end, repelling Troy Deeney’s header from point-blank range.
Two minutes later, Mason wasted another good chance when he latched on to Alex Baptiste’s long ball to round Almunia only to take it too far and the opening was gone.
The goal was coming but it Jutkiewicz – with his third in four starts – who broke the deadlock when he slid in to convert a low Jay Spearing free-kick from the right on 35 minutes.
Just before half time, the lead was doubled when Mason finally got his goal.
The Cardiff youngster was quickest to a header back into the danger area from substitute Neil Danns, who had earlier replaced Darren Pratley, to slide the ball under Almunia.
The second half saw more of the same bright play from a Wanderers now oozing confidence rarely seen on home turf.
Danns saw an acrobatic effort saved while Mason was again denied inside the box by Almunia.
But they settled for two in the end, as well as a clean sheet and maximum points as they completed a first league double of the year against the Hornets.