In my case the airline will be Aeromexico, and it would be from Shanghai, China to Tijuana, Mexico, and the flight numbers are
But the dates could be pretty much anywhere from August 2016 up to six or even more months later than that.
In my case I'd be spending up to a year mostly in China and nearby Asian countries and taking a side trip to Mexico for a couple of months at some time within that, based on when prices are as low as I can find.
But I'm looking for a general technique that anybody could use to find flights.
I've tried Adioso, Momondo, and SkyScanner but they're all very inflexible and incapable for this kind of thing, unless I'm missing something.