MacDonald struck just before the interval reacting first to Cleveland Taylor’s whipped cross to slot home at the near post.
Weston wrapped up the points midway through the second half when he latched on to MacDonald’s through ball to shrug off two defenders and drill low past the keeper.
Stockport’s on-loan Reading striker Nicholas Bignall was the visitors’ main threat, twice testing Bees keeper Lewis Price.
But Paul Turnbull came closest for County with a 25-yard volley brilliantly tipped over by Price.
Bees forward Carl Cort wasted a chance to put the game beyond doubt when he headed straight at the keeper from Weston’s precision left-wing cross.