I wouldn't buy those all-in-one, "ready to burn"-type grills that has the charcoal and grill together. It is adviseable to use good quality lump charcoal, 100% carbon. Chimney starters to get the coals lit. Maybe some small steel buckets to put the coals in after they're glowing red and emitting no smoke. Then the buckets are placed inside and given time to fill the car with CO. Cars are more dangerous because you're limited where you can place the buckets of coals which will be extremely hot. It's harder to seal all the leakage points in a car, too. With no meter, it's about impossible to know if the necessary amount of CO would be in the space. There's a formula to use .135 kg of charcoal per each cubic meter (m³) of volume of the space being used. That's a minimum though.
You doing this in the mental condition you seem to be in, just trying to do this "shooting from the hip", so to speak, with no real planning, researching, studying, understanding, is probably going to result in a failed attempt, probably messing you up big time, maybe rendering you a vegetable. I wouldn't advise doing this in the haphazard way you are contemplating doing it right now. It's probably going to go bad for you.