After being held to a draw by the League One club Griffin Park, it looked as if the Bees would frustrate the Blues once more.
But, Juan Mata put the home side ahead after 54 minutes, before Oscar, Frank Lampard and John Terry secured their spot in the fifth round.
Benitez, whose team will face Middlesbrough next in the competition, was happy with his side’s patient approach and felt they got the reward their play deserved:
“Credit to them because the first half they were working very hard, but afterwards it was a question of time.” He told Sky Sports.
“We knew scoring first could be the difference. They would be more open and we would have more space.
‘I’m pleased to score four goals and create chances. I’m really pleased with Oscar and Demba Ba did a great job keeping them busy.”
Lampard’s strike, Chelsea’s third of the afternoon, took his tally for the West Londoners to 199.
Benitez was full of praise for his midfielder, who has been in fine form of late:
“The team is doing well and Frank is on fire so he is scoring goals and that is good for him and good for us.”
Chelsea have now won their last three matches, following positive results against Wigan and Sparta Prague in the Europa League.
Benitez is happy with the run and keen to keep it going:
“In football you have to win games and for a top side it is even more important because everybody expects you to win every game.”