I would recommend using a Destiny Knot. As you might know, normally, only 3 IVs are passed down, so hoping that the game chooses the exact 3 you want is a time-consuming process. But if one of the parents hold a Destiny Knot, 5 IVs are passed instead, which naturally increases the chance of getting the 3 you want. Additionally, it stacks favorably with the Power items; the power item will ensure you get 1 IV, and then the game will still choose 4 others. I believe it can be found in the Battle Tree for some BP.