you should be able to paint a car with about five ltrs. i use acrylic laquer as its much more forgiving than 2 pack, with acrylic you will need the paint and about the same again of clear gloss then you need primer surfacer. i use a scorpion gravityfed gun and i have used cheap guns before and not been able to tell any diference, although i am only a hobbiest painter, not a pro.