It took the visitors just four minutes for the visitors to take the lead, Danny Hollands firing home after Jack Whatmough's initial header hit the post.
It was 2-0 in the 21st minute when Drennan headed into an empty net from close range following Jed Wallace's chip over the on-rushing Dagenham goalkeeper. He thhen doubled his tally for the afternoon in the 57th minute with a superb 25-yard half-volley.
Daggers captain Abu Ogogo grabbed a consolation against the run of play for the hosts in the 34th minute, heading over Trevor Carson after Medy Elito's initial shot was superbly saved by the keeper.
But Wallace put the icing on the cake, tapping home with three minutes remaining following a woefully short back pass from Luke Wilkinson.