You would have to abuse your ID/SID. Which can easily be done. So don't rely on luck to get you the correct ID/SID as 99% of the time you'll just come out with time wasted. Along with a lot of tears :POk so this means that I should restart my game and see if I'm now able to get it shiny and almost flawless? I won't mind to delete my data if is that necessary.
You have to have RNG reporter, there will be a tab to the side "Pandora's Box" click that.
Find the PID of your spread, put it in there (don't add a specific Trainer ID, as it will just most likely not give you any results). Add a year, than add a minimum delay and a maximum delay. Click "Find Compatible Seeds" and when it's done searching, it will show you all the results that can make that PID shiny in that year with between those delays.
My first suggestion is attempting at ID/SID abusing first, to see what kind of a delay range you can hit effectively. Without rushing, than adding those numbers into the minimum and maximum delay ranges.