Depends on the brand of paint. Cheaper lines will take more coats to cover. High end lines will cover in 2 coats. Cheaper paints might take 4-6 coats.
Now if the entire car is primed, you may have a hard time seeing coverage. But when cleared and out in the daylight, you may see color differences at overlap areas such as door/fender and door/ quarter panel.
I painted mine with DuPont Chroma Premier. It costs a bit more than regular chroma-base but has different binders that cover faster. So 3 coats was all I needed, followed by 3 coats of DuPont clear.
I didn't spray inside the bed but did do the door jambs. I used about 2 quarts and 1 pint (2 1/2 qts) of color thru a Sata Jet 3000B 1.3 HVLP gun. The gun is a bit expensive but cheaper guns will use more paint.