>>718689218
It depends on the game. For many games you can just soft reset.
The easier game to do that in are Soul Silver and Heart Gold because you can save in front of the pokeballs and you can see from the preview if one of the starters are shiny, it's about 3 checks every 30 seconds per copy. If you do it with 4 copies you're doing 24 encounters per minute or 1440 encounters per hour, which means it would take on average less than 6 hours to find a shiny. With one copy of the game it would take on average 24 hours to find one.
Not bad all things considered.
