Boss Battle Mode

[Epsilon52]

Okay so im completing all of the challenges and im now stuck on The boss battle ones. For some reason Brawl wont let me use any of my hammers to break the boss challenge squares...anyone know why?

And as for actually going about it on Hard and above i need alittle input on which characters would be best to complete this.

Only answers from people who have actually done these...obviously...

[Pit_the_Angel]

You can't use your hammers on the hardest boxes. Like those.

[Eternal Yoshi]

On Very Hard, I used Snake's Dair and Nair to do the job. Toon Link's Nair(Provided you can land both blows) works well too.
On a side note, Lucas can absorb Master Hand's missles. Not sure about Ness.