Yeah, I always RNG my parents before I breed, because I usually need them to pass down a different IV every time. So first I find which egg IV frame I want to hit, so I know which IVs I need to be passed down. Then I switch the method to Method H-2 and set IV filters for which IVs I need my parent to have (and which nature, if I'm using an everstone). Then I catch the parent(s) and use them for breeding!
Does that make sense? Like, there's not a single spread that will get you a 30+ Ditto in all stats (well, there is, but it's probably on a super high frame that will takes days to hit) so you usually have to catch new parents for every breed.
Edit: I have more than one Ditto because there's not really any good IV spreads on a low frame. I just catch parents based on the stats I need to pass down!
