Legend of the Guardians: The Owls of Ga'hoole

This was the last (non-platinum) trophy I got. The reason being that the shinies from separate save files don't count towards this trophy. So, after I finished the game with all four owls, I loaded up the save file that had the most accumulated shinies and started my grinding. On the plus side, you don't have to have 4200 shinies at one time; i.e. you can spend your shinies to unlock all of the battle armor with no penalty to this trophy.

I found the best way to rack up shinies is to play your favourite survival challenge. I liked the one from the bonus level in The Forest Kingdom of Tyto. If you go this route, just make sure that you keep your combo up, because that gives you a multiplier bonus for your shinies.