NOTE: YOU CANNOT RESPAWN ROAMING POKEMON OR LEGENDARIES IN DIAMOND AND PEARL.
THE LEGENDARY WHATEVERS
I advise to do a normal or static hunt first before trying this, TECHNICALLY? this is just as easy. the catch is if you fuck up you have to do it all over again bc the game autosaves after you beat the champion lol.
"Oh no, I already released the [insert arguement about whether they're cats or dogs here] into the overworld and they're not shiny! What do I do now?!"
Step 1 - Kill the beast
You've gotta knock it out, so that way when you beat the E4/champion it respawns into the world with a new PID. You only need to knock out the one you want to hunt, you can only aim for one shiny per reset anyway, and any that are still on your map are going to be helpful to the RNG process.
Step 2 - Kill the E4
Okay don't kill them because you might need them alive again if you fail the RNG. also this isn't a creepypasta i don't think you can do that. don't beat the champion yet, save infront of them.
Step 3 - Set up the RNG
Step 3.5 - The details
OKAY ACTUAL DETAILS AND RESEARCH. [i will put that here]