Darren Dods claimed Brechin looked like 11 strangers at times as they slumped to their second cup defeat in a week without a goal to their name.
Gerry McLauchlan, who spent five seasons at Glebe Park, fired Ayr ahead in 12 minutes. And it was game over on the hour when Paddy Boyle beat Graeme Smith with a stunning strike after the keeper had done well to parry from Ross Caldwell.
Player-boss Dods admitted: “We were disappointing in the first-half when we tried a new system which didn’t work.
“To lose the first goal from a set-piece was also disappointing as we had worked on them during the week.
“The second goal was a bad one to lose and knocked us back although we had a couple of late chances.
“We need to make ourselves harder to beat and at times we were like 11 strangers.”
McLauchlan’s strike came after the City defence fell asleep at a short corner. Martyn Campbell sent in a powerful header which was blocked but McLauchlan followed up to slam the ball home from six yards.
Ayr dominated as Brechin barely threatened the home goal but James Dale wasted a great chance soon after the break when he headed wide then Craig Johnston shot over on the turn.
But just as Brechin seemed to be getting a toehold in the game they were blown away by Boyle’s fizzed finish.
Craig Molloy and new signing David Weatherston entered the fray for City and there was a late chance when Johnston made space at the edge of the box and sent in a shot which Greg Fleming blocked with his legs.