How do you do all that big giveaways

[Chocolatte_Banane_Pokemon]

I have seen a lot of pokemon giveaways like: 6IV´s Shiny Dittos or giving other pokemon, but in almost all it says that they have 100.

I want to knowhow do the people do those giveaways of 100 exactly same pokemon. Do they/you take a long time training them or they just powersave or pokehex or something?

Im planning to do some giveaways, but even if I know how, I dont know if I would have time. Please reply