Okay, now like I said before, you wuld like to hatch 150 eggs without turning your game off. Now, as you probably know, Magikarp eggs hatch very quickly. So, you want to hatch a good amount of magikarp eggs, ideally between 100-120 (hatching in groups of 5, then releasing, to help count), then you want to hatch 50-30 eggs of the pokemon that you want to get a shiny of. Now the worst case scenario, you accidentally get a shiny magikarp (boo hoo). Anyway, you dont have to hatch 100 or 120 magikarps, you can hatch however many you feel is a good number, while leaving your game on and following the other rules, then proceeding to hatch whatever pokemon you want a shiny of. turn it off after 150 eggs hatched this helps ensure you get a good shiny frame.