I've come to love those two matches just because of one simple technique,
Empty Shorthops.
Empty shorthop around the place, and then throw in some bairs, and some more empty shorthops (works with ganon also).
The empty shorthops encourages them to approach, or it throws them off, and they'll shield while you're in the air, but drop the shield when you land. That is when you quickly shorthop backair or any other aerial/ground move.
Against marth this works especially well. Empty shorhop into their shield and the crouch. Usually leads to a free rest, or a couple of hits. Also, empty shorthop into your shield, and then punish their lag after they have hit your shield.
here's a couple examples:
Against Marth:
http://www.youtube.com/watch?v=dA9kJ1QNcpo (ignore the speed change youtube gave it...)
Against Ganon:
http://www.youtube.com/watch?v=VVDKaBogtjI
Once you get a Ganon in his shield, it's basically done.
To get him in his shield I suggest Fullhoping a bair or fair, then just land (no second aerial) in front of their shield and crouch (which baits grabs) and uptilt when they miss a grab, and just wavedash in and out of their shield. Even just shorthop backair torest into their shield works too.