Here is how I do it, and it works FAST!
Make the normal account, then start the game.
1.Go through all the beginning options (pick driver, message, and etc.) but do not select the card yet.
2.Buy a used car CHEAP!
3.Go into options, bottom of the options list is utilities. Click off the opening movie.
4.Save data in main menu of GT life.
5.Back out of game, and save the data to a flash stick.
6.Take flash stick out of PS3, insert into PC. Open up the flash stick using Windows. In folder PS3, you will see a folder called Savedata. Right click on the folder, select send to../Compressed(zipped) folder. Label it according to your dummy account (ie geezerdouche 1970 Bday Glitch)
7.Put stick back in PS3, start game
8.Select Bday card, if it what you want, send to main account, if not, quit game, reload the bday card save.
This saves me loads of time!!! If you zip up the bday card save on PC, you can always come back, and restore the Bday card save, and keep farming cars at a later date.
I make zip backups of every car I send to my main, also save ones I might want for later. I have 20 cars coming in 20 days from my dummy accounts