1: Start the game.
2: Select a play mode (single player recommended).
3: Alt+Tab and open the trainer AFTER the game.
4: Go back into the game and activate trainer. (listen for activated sound)
4.5: If this is the first time doing this, you may need to alt-tab again and follow the simple prompts so the trainer has the current version. If you do, let the trainer do this, close the game, then follow steps 1-4 again.
5: Select a song and load it. Once the song is loaded, THEN activate the cheats you want to use.
6: Turn off the cheats when the song is over. If you leave them on, the game usually doesn't crash, but it does increase the chance of it crashing by leaving them on.
Just repeat steps 5-6 for every song. This still works, I was just playing it today. 2 hour survival. I just let myself die after the folder looped to the beginning again, so you can go for as long as you want during the songs.