Originally posted by Dr Flibble
Tested it. This is an insta-plat. After you load the game wait about 30 seconds or so and trophies will start popping. All you have to do is go to the shops and level up the scrapper hammer to get the last trophies. Make sure you re-sign the profile!
edit: It also works with the EU version of the game. You don't need to re-region.