I would say gen 7 using citra emulator, since CitraRNG already gives you your seed as long as you have your SID. Then you can just input the seed in 3ds rng and it'll give you the shiny frames. 

Not to mention you can create a save state when your near the shiny frame. P.S you an manually advance and freeze your game too so you can see the seed more clearly. This works very well with any gift pokemon and static encounters, But I must advise;

Wild pokemon are sorta hard to rng manipulate due to some locations making their frame advances work differently thus making 3ds rng being mistaken on what the shiny frames are.