Hayhurst, 19, scored from a tight angle in the seventh minute from Lee Holmes' cross to cancel out Adam Chicksen's early opener for the Dons, who have now drawn four successive games.
Grayson said: "We got off to a poor start with a mistake but from then on the players showed endeavour, work-rate, a good attitude and they've put their bodies on the line when they've had to.
"We played a decent passing game at times, we just lacked that little bit of quality in the final third when we were counter-attacking.
"We spoke to both the wide players, telling them when it's going down the other side to get in at the far post because a lot of the time defenders switch off.
"It was great play by Lee and Will burst in there to finish it off.
"I'm delighted he's got two goals in two games and his confidence will be soaring game by game.
"But it's not just his goals, it's his overall work-rate, helping out with the defending and the attacking side as well.
"I'm delighted that we can go back to Deepdale next week trying to get three points, still unbeaten, and try and extend that run forward."