So I finished the main game, completed every level, collected every star coin, I even
finished the secret star world and collected every moon coin
Right now I have about 57K coins, it seems absurd to repeat this process 20 times to reach 1M coins... I know playing the game in coop yields more coins, but unfortunately I'm the only one I know who owns a 3DS and lives in my vicinity.
So how can I reach the 1M coin target? Do I repeat endlessly the rainbow levels? Is there some sort of glitch? Or am I missing some special game mode which yields unusual amount of coins?