Tunde Owolabi's 59th minute strike separated the two sides but, in truth, Brig deserved far more.
Kieran Charnock saw a header cleared off the line by ex-Brigger Adam Dodd in the first half, before Michael Fowler hit the post in the 90th minute.
The hosts started the better of the two sides in front of a crowd of over 1,500, and their first chance came when Tom Dean headed the ball straight at Lloyd Rigby in the Brig net.
Joey Collins's side quickly gained a foothold in the game, though, and Fowler's curling effort on 24 minutes drifted just wide of the right post.
Three minutes later Charnock met a Brig corner and was denied only by the boot of Dodd on the goalline, before Adam Sumner's lofted through ball played in Fowler only to be denied by the outstretched leg of FC 'keeper Paddy Wharton.
Brig then came even closer to opening the scoring when Tom Walker's deflected cross hit the outside of the post and went wide, although they were nearly hit by a sucker punch.
FC United quickly countered from the resultant goal kick and Rigby was called into action to block Alex Curran's effort on goal from the edge of the box.
Alistair Waddecar then had two chances shortly before half time - the first a curling effort similar to Fowler's which fizzed past the post off his right boot.
The second resulted from a great lay off from Forbes who held off two FC defenders inside the box, but Waddecar's snapshot again went wide.
Brig's number seven had the first chance of the second half, an effort from distance going over after good work in beating several defenders.
But FC United were beginning to put the pressure on and started the second period at a higher tempo, a driven cross from the right just out of the reach of the onrushing Owolabi.
But the former Radcliffe man opened the scoring five minutes later, finding space on the right hand side before cutting in and seeing his effort deflect and go past Rigby at the near post.
Apart from an Alex Curran strike that fell into the gloves of Rigby minutes later, however, it was Brig who had the better of the second half chances.
Forbes played Waddecar through but his effort from a tightening angle was well blocked by Wharton, before Forbes himself had a shot from distance that fizzed past the post with the 'keeper seemingly beaten.
The only downside of Brig's since the opener so far was that they hadn't scored, but then there was concern when captain Matt Lawlor went down with a head injury.
Lawlor went off and was replaced by Gary Pett as Joey Collins's side continued to put pressure on FC.
In the 89th minute, Michael Fowler did exceptionally well to control a through ball and round the keeper but his effort hit the outside of the post.
That was to be Brig's last chance of the afternoon, one that they can feel unlucky not to have taken at least a point from.
Match reporter: Ryan Smart (@RSSport2)