1º Create a GCT File with the code:
Enable 50/60Hz Mode Option v2 [Ralf]
04008544 38000001
04008548 900D00F8
2º Put the GCT File in the same folder as the game, with the same ID; in this case USB/Games/GLMP01/GLMP01.GCT (Luigi's Mansion Pal). You need the file Kenobiwii.bin in a folder named sneek on the root of the USB, so USB/sneek/Kenobiwii.bin
3º I use Nintendont Launcher, so I load the homebrew through the Homebrew Channel, and go to the USB menu. Press B to access the options, and turn on
Cheats.
4º Launch the game. It will start at 50hz first, with the red logo of Nintendo, and when the game goes to the Title Screen, a question about changing the video mode will pop up. Answer YES and that's pretty much it, you'll be playing Luigi's Mansin Pal with 60hz.
I did nothing more than that.