If you need a certain spread to be shiny, you can use that seed and try to achieve it when starting the game. If you want more than one good spread, use this
sheet by OmegaDonut, it has got seeds which give groups of good shiny spreads.
To hit the needed delay and seconds, you have a good guide at the end of this
post by Romsstar. He says that his usual delays are between 5730 and 5740 but mine are actually around 3600 so the calibration phase is really important. I would advise that you start the game as fast as you can and then save and use an AR to find you're SID so that you can know exactly what delay and seconds you hit (read Romsstar post to know how to do this with ID Finder). You only need to do this once. Afterwards, proceed with the calibration. What did was use a timer and get comfortably to the screen before the ID/SID combination is generated. When the timer ended, I pressed A, input the ID in the program and figured out my delay. I did that a couple of times and then searched for a time that would give me a ID/SID combination for that group of spreads within the delays I had figured I could easily hit.
Hope I helped^^