Fulham were without their World Cup players and the injured Andy Johnson, but still named a relatively strong line-up for the match, which doubled up as a testimonial for Bees skipper Kevin O'Connor.
Chris Baird broke the deadlock with a 25-yard low drive which beat off-balance Brentford 'keeper Richard Lee after 14 minutes.
The Bees were handed a way back into the game seven minutes later when Stephen Kelly clumsily fouled Charlie MacDonald in the box.
Referee Keith Hill pointed to the spot but David Stockdale saved the striker's drive.
Brentford were made to pay for the miss soon after when David Elm curled a 20-yard strike inside Lee's right-hand post to double the visitors' lead.
Damien Duff raced through to poke past Lee on the half hour to make it 3-0 as Fulham continued to dominate possession with some neat passing.
Gera, one of four half-time substitutes, made an immediate impact by playing through Johnson, who coolly rounded the keeper to make it four just after the break.
They soon found themselves five up when Gera's cross was met by Simon Davies at the back post.