For the Line Trial, use Kirby. Get the Burning power-up and when you get to the part where there are a bunch of ledges and you must get to the top, keep tapping Kirby. He will dash into the walls. Slowly but surely, he will climb up the walls. You must use some ink to get to the end. Once you cannot do this anywhere, get rid of the Burning power-up then use two simple lines to reach the goal. You should make it in better than 800 ml if done correctly.