A dream home debut from Ranegie saw Watford claim a big victory over an abject Blackpool who are unable to buy a win at present.
Without suspended pair Jack Robinson and Tony McMahon, Blackpool defended criminally all afternoon and the score could have been worse for the horribly out-of-form visitors.
No-one challenged Ranegie or Deeney as the strike partners were allowed to claim two goals each with minimum effort.
The Seasiders arrived at Vicarage Road unbeaten in five visits to the now three-sided ground, but their more recent form was less encouraging with no wins in 15 games.
That familiar losing feeling did not take long to engulf the Seasiders.
Daniel Pudil curled in a corner and home debutant Ranegie rose unchallenged to power in a header from the centre of the six-yard box.
They have not triumphed after conceding the opening goal all season and never looked like doing so here either.
They had already had one escape when Deeney sprayed his shot wide from a great position, after his tricky footwork deceived Gary MacKenzie.
Watford rose to the brink of promotion last season playing a swift, short passing game installed by Gianfranco Zola.
But, despite replacing Zola with fellow Italian Beppe Sannino, the Hornets now play in a more typically English-style with Pudil and Ikechi Anya crossing for two powerful strikers - Ranegie and Deeney. That combination doubled Watford's lead after 34 minutes.
Daniel Tozser fizzed a pass into Deeney's chest, the striker exchanged passes with Pudil before firing in his 50th Watford goal thanks to a deflection lifting his shot over stranded Matt Gilks.
Soon after Gary MacKenzie conceded comfortable possession under pressure from Ranegie, who received a return pass from Cristian Battocchio and slotted home with scarcely imaginable ease on 39 minutes.
Ranegie appeared against Roma and both Milan sides this season for Udinese and it is fair to say found MacKenzie and Kirk Broadfoot more obliging company.
Worryingly for interim player-manager Barry Ferguson defending has been his side's relative strong suit this season, as they have only managed seven goals during their long winless run and their top scorer now plays for Crystal Palace.
They finally found the target early in the second-half, but Ricardo Fuller's powerfully-struck was at a comfortable height for Manuel Almunia to parry wide.
However, Watford sealed a fourth consecutive home win with Deeney's second on 74 minutes.
No defender was anywhere near him as he collected Battocchio's pass and curled a lovely shot into the top corner.
Deeney had the ball in the goal two minutes earlier, but at least this time Blackpool's defenders could attribute the excess space he was in to what looked like an offside position.