F-Air is a b*tch for Ganon alright, but Ganon has a pretty solid defense around some of MKs approaches. F-Tilt, DA, and wizkick should all be used often but intelligently in this match up, as they all defend well against MKs air game. F-tilt can snuff f-air, DA can cut through it if timed correctly, and wizkick is just plain fast and destroys low level airdodges and short hops.
Make sure you're getting a good amount of gerudo in too. In this match up, gerudo gets you kills at 85% and can get you 50+% "strings of attacks. At early percents, a landed gerudo leads into d-tilt. After you land the d-tilt, MK is put into a tough position. Of course he can try to immediately attack but that just gives you shield grab. After the d-tilt you can follow up with another gerudo, dash attack, wizkick, or grab. At 0% or around there I just like to use another gerudo as it resets and I get another d-tilt. After that second d-tilt it puts him up higher, which actually puts him at a little bit more of a disadvantage. Just wait, you can punish any attempt he makes. He airdodges, you can gerudo, DA, wizkick, or even u-air. He attacks and you have the same options. He DIs or does nothing, you wait or run and follow up.
A lot of this match up is being very patient, trying to get damage off of punishing Meta's approaches, and looking for gerudo, as it does everything against meta. Just remember not too approach with gerudo...very bad. I'm having success punishing a shielded tornado with Gerudo too. I'm trying to figure out the right DI if you get caught in it, but I'm not sure yet. Oh and multi tap horizontal DI works well against his u-smash.