In my personal experience, as a hobbyist, I've found it better to do the time consuming prep work at home and leave the painting to professionals with the proper experience, equipment and facilities. It can take me days to carefully strip a frame. I have a collection scrapers from broad to dental pics that I use to remove paint chemically and I'm very careful with abrasives. It would be crazy expensive to pay someone to do the stripping, prep job I do on a frame. And it would be crazy expensive to buy the tools and build a facility that could do as good a job as the body shop in town.