I've only been using the dittos to transfer natures to the initial mother, much faster than trying to synchronize for parents each time. But Smeargle is indeed the ultimate example of why safari dittos aren't as great as many believe, because of his ability to have any egg move combination via sketch. And being able to spread IVs from one egg group to another is indeed very easy now. Chingling can spread IVs to the Water 1, grass, mineral and fairy groups. Trevenent (grass) can breed with bulbasaur who in turn can spread to many egg groups via his connections in the monster group.