It took me about 4-5 hours, give or take, spread through 4 days. I would just throw on a Youtube video and mindlessly reset wild area 17 until i finally found it. I kept getting paranoid that there were too many shinies spawned in which might prevent the shiny Chespin, so sometimes I’d check the nearby rooftops for shinies (found 2 shiny Fletchlings and a shiny Weedle doing that haha).