I just finished this one. I used fox and most of it was easy.
The match against Dedede and Metaknight with kirby on my team took me like 10 continues.
Team Lucas and team Zero suit Samus were both easy thanks to the reflector shield.
Giant Wolf and Giant Yoshi went down surprisingly easily. I just stood in place holding up and pressing the crap out of the A-button until they were around 200% then up smash.
The 3 on 1 match gave me Ganondorf, Sonic, and Capton Falcon. That was a major pain in the arse. After another 10 continues, I ended up winning by running to one edge of the screen while they fought. Then when they got close, double jump and fly across to the other side of the screen. They did a good job of killing each other off. A few minutes later all I had to do was put the finishing hits on Ganondorf.
Master hand was INSANE compared to Boss battles on intense and SSE on intense. In Boss battles, it takes 8 of fox's downward arial attack to kill him. The Master hand I just saw took double that. And on top of that, he is faster than before.
So, having done this. Here's my advise-- Take a buttload of coins with you. It costs 100 every time you continue. The fastest way to get coins is at the Ruined Hall in SSE. On intense, you get anywhere from 35 to 42 coins every time you beat it. It takes just over a minute to do, so in an hour you should have enough for 20 or so attempts at classic mode (and if you use "+sticker drop" stickers, you get a lot of rare stickers, too).
The CPUs are like level 15. They air-dodge, roll, spot-dodge, and every other kind of dodge. They even chase you off the edge of the level like the cruel alloys. Make sure you can do all of this, too. Also there are some items they will pick up and some they won't. Pay attention to the stuff they go for and beat them up as they go for it.
When you get to the 10 vs 1 team battles and the giant opponents, find a good move to spam.
Practice on Master hand in Boss battles on intense. I can kill him without getting hit, and the Master hand in Classis mode got me up to 150%.
Thats pretty much it. I hope this helps anybody that was having trouble with this one.