The pokemon with the nature you want should be holding an everstone.
If you want the IVs... Destiny knot. Alberto Del Rio approved :
I will have to see what I can do with this. I really want to get some good mons going to use online. I played a singles battle with a Twitch streamer and got blown back... Someone even said "DELETE this battle" LOL Referencing my BrockLespurr mon. haha