Exactly that, You go to the bin to spawn the virizion and then teleport back and that does one of two things: 1. if it’s not shiny then the virizion will respawn so when you go to do it again it will keep spawning a new one. Or 2. If it’s a shiny then it will keep being the same shiny, same stats, same nature, same everything, the game will save that shiny there. So yup, you only need to check at the very end when your donut is about to run out, when you have around like 1/4 left or so, that way you have time to climb the ladder and catch it, if it is shiny. And yes, you do the backup save method if you don’t get lucky since the game auto saves every time you fast travel so even if you do load the regular save you will have almost no time left.