Peter Kioso's first-half brace set up an impressive and emphatic win before Ryan Watson netted his ninth of the season late on.
The Cobblers remain four points from safety with three games to play.
"It was a good win," said Brady. "The two goals came from two set-pieces and that was something we worked on in terms of trying to free up Pete in the box.
"The delivery was on point and he timed his arrival well and I thought it was a very strong performance in the first-half.
"We stepped on when we needed to, we closed off lines and we got in a few times in the first-half and we also had to weather a few little moments.
"We came out in the second-half and we sunk too deep but that's the story of our season a little bit so we had to change our shape and that allowed us to press on a bit higher.
"I thought thereafter we looked a lot better and it was a good win for us."