The Ability Capsule is a new item this generation. You can only use it once. It costs 200 BP in the Battle Maison. It will switch a Pokemon NORMAL abilities if there are 2 of them. It does NOT work to get the hidden ability.
Your doing better than I am then ...I bred I don't know how many boxes of Marills trying to get a flawless one!
But I also keep reminding myself yes each generation they make breeding the pokemon you want easier but they always leave that element of chance. Sometimes you get very lucky and most of the time, for me at least, not so lucky.
So I'm only about 1 step ahead of you...
Aron with its Hidden ability can only be obtained in X and by horde.
the problem with hordes is you can't use trace to identify a pokemons ability and few have the hidden ability
So you're left with catching a LOT of pokemon or
Finding a pokemon that can learn Skill Swap (Duosion, Spritzee, Carbink or Smeargle) (oh the reason I can tell you all of this is I just looked it up day before yesterday)
Find a pokemon that know something like Entertainment I think is the other move that switches or tells you what the opposing poke's ability is and I think it is a move so you can focus on individual pokemon in the hord...if I recall correctly Audino.
or the easy way is to trade someone for it Varanus is good