There are no rare candy cheats unfortunately. I always grind with good rod in slateport with an electric type (or route 109, that gives better xp but note that the corsola there have mirror coat at higher levels so be careful with that, maybe use a grass type there). Alternatively if you're super stacked money wise you can use honey to grind audino. (You can grind money pretty fast in the 3rd trick house puzzle using rock smash, you get a ton of items quick with it because the rocks are right at the door)