I had discovered a fastest way to get your code!
You only have to run the course 1 time, and when you finish it appears the last 5 users that played the game, select one, wait until the grey windows appear and without select any other player or friend write a reason to grudge and press NEXT, it will appear a message that tells you the Grudge has been created. Ok now close this windows with the cross on the up right corner, don't press NEXT or VIEW GRUDGE.
This way you will return to the end of run screen, and then you can select another player from the list of Lasts Players and do the same, four times.
So you don't have to play the mini-game four times! It works!!
PD: Sorry for my poor english.
Salu2