The former MK Dons and Chesterfield winger found the net in the eighth minute and despite Robbie Simpson hitting a post after the break the Shots were worthy winners.
Aldershot had taken an early lead at Griffin Park and wasted little time in repeating the trick as Small raced onto Glen Little’s through ball and fired beyond Richard Lee for his third goal of the season.
The pace of Small and Jermaine McGlashan troubled Andy Scott’s side for the remainder of the half and when the duo combined after half an hour, Aldershot’s lead seemed certain to double but McGlashan’s volley skewed wide.
The Bees’ only genuine chance of the first 45 minutes came through Charlie MacDonald but the 29-year-old’s effort was firmly blocked by Aaron Morris.
Scott had clearly got into his players during the interval and within three minutes top scorer Simpson might have restored parity but found the inside of post after MacDonald’s cut-back. Myles Weston then flashed a shot wide of Jamie Young’s goal as the Bees continued to fail to work the Aldershot keeper.
Despite the introduction of Nicky Forster, Brentford’s late pressure failed to yield an equaliser as Aldershot went through to book a date with Conference South outfit Dover.