Ganon's DD is nothing like marth's, but you can DD against all of his approaches in order to bait them, except for dtilt and him just running up and grabbing. Even then, if you react from DD with a...
-AC bair into dash away and immediately dd again
-WD away into another DD
-dashjump away into bair or waveland where practical
...You can download some habits for free.
The bair obviously kills approaches and is safe when spaced/AC'd into dash away
The wd away into DD escapes lots of stuff and you can grab an approaching nair/react with anything
The dashjump away is a bait, if he follows you can ff and bair or waveland approach if he's not ready
The key is reacting in time so you can remain safe. If you let him get too close, you have to go for a desperation read. You can can still often bair his approach, but you can also DD into shield while facing him. As soon as you shieldstop keep holding forward or forward and down, which will make your uair oos more applicable and get you more shieldgrabs. You can also DD into crouch when he's gotten too close and CC his ass, but when he starts grabbing these won't work.
And at any point he sh rising fairs, you can side-b him from your DD. I know
tm
can react quick enough lol. The DD occasionally baits sh rising fair from good marths. You can throw in a side-b to punish nair landing lag too, the reward is high and they're not always ready.
Then you always have your standard aerial baits, retreating fair for confident reads, and empty sh waveland. If you're using all your tools and downloading his habits, you'll almost always find the openings you need to put him away. There's just little room for error. Play neutral smart enough to frustrate him. You CAN take away a good bit of the effectiveness of his range with smart play and quick reactions.