I must have sanded 30-40 cars working after school - all by hand. I would wet sand with 320, then switch to 360-400, then rinse. Then the car would be primed, sanded again, wiped down with a solvent, taped, wiped down with a tac rag and then sprayed. This was the 70's and we're talking single stage enamel or lacquer. If you learn the technique, you won't have issues with sanding by hand - other than your hands, especially your fingers will be extra sensitive. I think as far as wet sanding today with the 1000-2000 grit paper, you would have less of a problem with uneven pressure from your fingers since the paper is so fine. I just haven't had a detail that required sanding - yet.