Chinch bugs in Canada? I thought they were a problem in Florida. Oh wait--you posted the question in August.
Perhaps you need to get the customer to overseed with a superior variety with high endophyte levels for insect resistance...like...Dasher.
Secondly, plenty of water and fert during summer stress periods will cause your grass to recover much more quickly.
Warm today--hope you don't have to do any mowing or actual work today. In fact, I hope it snows, because chances are, you need the income from snowplowing.