To do this, you will need 3 controllers and your keyboard. Connect all 3 controllers, then open multiplayer, select 4 players, open grand prix, and select your cup. From there, select your racers. For your character, select CatDog with Ed & Bev Bighead as your chief, Really Really Big Man and Gary as your pit crew, the Monster engine, Log wheels, and Flower as your exhaust pipe. For players 2, 3 and 4, select Angelica, Squidward and Shredder with any build (They're the most annoying to deal with, and this makes it so they won't bother you in the races)

With everything now set up, begin your race, and just race as normal. Do not carelessly use your chief skill on the final lap, save it until the end because the CPU's can and will randomly get in front of you, that is when you use your chief skill, it will save your races a lot. When you see a Jellyfish approaching (you will see it earlier on the split screens of the other players), if there is a CPU nearby, slow down so the Jellyfish targets them instead, then proceed when it hits them.

Using this method will still take a few tries, but this will make your experience significantly easier. I hope I helped! :)