I controlled both players on touchscreen, I made the buttons turn invisble and remembered the locations, this was fun so I'll make a new video on it soon.
y'know I wish someone would make a multiplayer rom hack that uses the multiplayer infrastructure already in the game to allow up to 4 player simultaneous star collecting in the campaign.....
It's on one console, I'm using an emulator in this video while controlling both players, left hand as P1 on the left half of the controller and my right as P2 on the right half of the controller.