Surface rust is a bigger PITA than you think. To deal with it correctly, the area needs to be blasted and treated, not just sanded. otherwise, the rust will come back. This can take some time to do correctly. As for dealing with straight rust free cars needing a respray, I did a quickie respray on my pizza delivery truck a few years back. It was only 6 or 7 years old at the time and had never left Florida, so it had no real rust to speak of ( a little surface crap in the bed where it was scratched). The only real issue was peeling white paint, and 2 dents that in total maybe took me 3 hours to fix. However, the peeling paint issue took FAR longer to fix than the dings and dents. All totaled, I spent a month doing prep to fix the peeling paint-strip, prime, block, etc. I didn't even prime the whole truck either, just the repaired areas. Plus, it was not intended to be perfect, just a fresh coat of white single stage urethane so it would not look ratty to the cops and customers. Understand that even minor bodywork takes a lot of time to do properly on a car with a failed finish. Most of the times, fixing a dent is far easier than fixing bad paint or surface rust. After all, I spent 4-6 months blocking and perfecting my Cutlass and only an afternoon of that was fixing dings and dents.