I bought a
Eastwood Contours II Kit a few years back and they claim it only uses 4.3 CFM @ 30 PSI. I can’t prove their claim, but I did a complete repaint on a unnamed auto two years ago and supplied air with my 45 year old Craftsman 20 gallon 220v compressor that puts out somewhere in the vicinity of 8.5 CFM @ 40 PSI. The compressor kept up with the gun pretty well and even cycled on /off a few times. The paInt was midnight black base with a clear over top and it came out absolutely beautiful.
I think the way Eastwood gets that low CFM rating is the Contours Il gun puts out less paint, so it takes longer, but for a backyard mechanic like me, it worked great.
I think my setup is the minimum required to get a decent paint job.