Master rank is extremely easy, basically get any pokemons contest stats to the maximum. Equip the scarf for the right contest these can be found in slateport city from the chairman of the fan club.How do you get master rank in pokemon contests? Do you have to go to every town's contest hall? Is it easy to get master rank?
Also, what's the best strategy in singles and multi battle battle mansion? Is that easy to win?
And use the moves rest and sleep talk. This wins you all contests without doing anything complicated.
As for the battle maison it's best to go with hard hitting pokemon such as CB dragonite, gengar, talonflame and any mega that's fast. Just click the strongest move, there really isn't much to it.