Trying to get modest? There is one thing I read on Bulbapedia saying that "From Emerald onwards, a Ditto or a female Pokémon (though increasing evidence points to BOTH genders) that holds an Everstone has a 50% chance of passing its nature to its offspring when at the Pokémon daycare, but only if both Pokémon and the trainer all come from a game in the same language" Also, if you catch them in the wild, having a pokemon with the ability synchronize givs a 50% chance of the wild pokemon having the same nature as the synchronize pokemon. It just takes, time, you have the same odds of getting every nature, and there are 25 natures, so you have a 4% chance of getting a modest nature.
http://bulbapedia.bulbagarden.net/wiki/Nature
