The Irish midfielder has responsibility for taking most of the Shakers' corners and free-kicks.
And his deliveries have led to five of their 11 league goals so far this season, including Efe Sodje's effort in Saturday's 3-1 win over Lincoln.
"I don't think there's anyone better in this division, but it only happens because he practices," said Knill.
"You can't take it for granted. Like anybody, you have to work hard at your art to perfect it, and Brian does that."
Sodje made it 2-1 from a 50th-minute corner by Barry-Murphy and left-wing corners by 21-year-old winger Mike Jones led to Bury's other two goals.
Knill encourages the Shakers to play flowing football although he accepts set-pieces are a big asset as they aim to maintain their unbeaten league start.
"We thought the next goal (after half-time) would win it," added Knill. "We thought it'd be from a set-piece as well, and fortunately it was a great delivery and a great header.
"The set-pieces from Barry-Murphy and Jones were unbelievable deliveries."
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