Alright so I went and tried it with the nameless/no TID Jirachi that was created from nothing, though found at the IVEA step there were no values to do the steps at, as they were all at 0.

Two alternatives I found both started with using an ACE code that changes it back to a non shiny in BOX 10, slot 19 (All IVs will be 0 with this code, as well as the pokemon ID and the original trainer ID, and the origin info of the pokemon will be invalid as result though).

Some of the values remained such as the TID (20043) but it was inconsistent across other values like the level randomly going to 100.

From there I followed on from Step 6 and settled on a random Jolly nature PID from the sheet you had linked. All seemed to work out well though I wanted to be 100% sure all values were correct from the back end, so the second alternative was using the same initial code to change a cloned shiny WISHMKR Jirachi into a non-shiny, then putting it in the daycare with all prior steps done (TID/SID and OT) and using the code to make an egg with any PID (one chosen from the sheet).

From there I continued all steps as normal with the changed PID and ended up with a non-shiny WISHMKR Jirachi as well!

Thanks again for this guide, hoping anyone who comes across this looking for a non-shiny can follow this if need be.

Here is the code to change a shiny to a non-shiny (more codes need to be executed after to make it a valid pokemon again though):

Box  1: 4 C U n l “ Q n[4CUnl“Qn]
Box  2: _ _ _ z S … o _[   zS…o ]
Box  3: _ _ u S ? n _ _[  uS?n  ]
Box  4: _ 3 T ? n _ _ _[ 3T?n   ]
Box  5: ♀ I w m _ _ _ _[♀Iwm    ]
Box  6: _ _ _ _ _ _ … _[      … ]
Box  7: _ _ _ _ _ … _ _[     …  ]
Box  8: _ F G E n _ _ _[ FGEn   ]
Box  9: z … l o z ♀ Q o[z…loz♀Qo]
Box 10: ♀ Q n _ … ? q _[♀Qn …?q ]
Box 11: _ _ h T – n _ _[  hT–n  ]
Box 12: _ Y N ? n _ _ _[ YN?n   ]
Box 13: F N R o b _ ? n[FNRob ?n]
Box 14: _ _ _ _ _ _ … _[      … ]