I spray pained my shed and fence panels. I have a special spray Gun for this and I also have to get the sprayable paint.
If its outside, you got to do it on a calm day. Not really a problem until you get close to walls, boundaries etc. Its much quicker than ordinary painting. But I have two gates and I'm going to paint them normally.
If I was hiring professionals I'd want them to use normal paint rather than spray paint. Normal paint will also clog the spray gun.
The spray gun has to be cleaned after each use as well.