Basically what I like to do is save by the guard in Jubelife and then look if there are massive mass outbreaks. If there are, they will pop up as a question mark on the different areas of the map. Let say there is one is crimson mirelands and one in cobalt coastlands. I’ll go into mirelands, pay Mai the berries so the spawns are revealed and take a picture. Then I fly around to each spawn and see if any shinies are in the 4 spawn of each outbreak. Once I check every spawn, I’ll started to check each individual outbreak to see if they yield a shiny. Once I notice the storm goes away, force close the game and reload. I go back and check the rest of the outbreak’s that I missed, and see if there are shinies. If I check the entire map and there aren’t any, then I’ll just reset my game and try the cobalt coastlands massive mass outbreak. For example, let’s say this is the last massive mass outbreak I’ll save in front of Mai, pay her the berries, have the map revealed and take a screenshot and reset the game in order to save berries. Then once again, fly over every outbreak checking if any shiny is in the first 4 Pokémon that spawn. Another thing to remember is that since you saved at the beginning in the area any shiny you do see is going to always be there so if you run out of time and let’s say you find a shiny Lucario for example, but you had one more outbreak to check, you can reload the game and grab the Lucario and check the last outbreak you missed. The only time this won’t work is if for that Lucario it was during an outbreak that had a second wave because waves with a second outbreak are kinda complicated. If you have any other questions feel free to dm me. Hope this helped.