Schumacher headed home Gregg Wylde's corner to clinch a point at the end of an entertaining encounter at Gigg Lane.
The Shakers have picked up just two points in their last four games but Shirtliff insists they have been worthy of far greater reward.
"It's becoming a bit of a habit that we're dominating teams and not finishing them off," said Shirtliff. "But you've got to give credit to the players for sticking at it for 90 minutes and never giving in.
"It's frustrating we're not getting the results but I'm a big believer that if you keep plugging away and keep sticking at it, your luck will turn and the results will start going your way.
"We just have to keep our heads, keep chipping away and hopefully we'll get enough points to stay in the league."
Bury fell behind within the opening minute when Aaron Wildig scored but Shirtliff was delighted with Bury's response.
He said: "It was a disappointing start and it knocked us on the back foot but from then on we bossed the game. We were in control, played some good stuff and created some good opportunities.
"The players stuck at it and didn't drop their heads. With a bit of luck at the end it could've been a 3-2 win."