I painted a Cessna 120 in 1981. It took 3 gallons of base color to paint the entire airplane. I had about a quart left over when I finished. I used DuPont Imron. An RV airplane has less area than the Cessna. Paint is heavy. I wouldn't put more on than necessary. I still own the Cessna and it still looks pretty good.
More than 30 years of owning airplanes have taught me that an airplane is near pristine perfection for only a short time after you finish it, then it's all downhill from there, no matter what you do. Maybe slowly downhill, but still downhill.
Been thinking about painting our RV-6, but it's still just thinking.