I have been painting canvasses for over 30 years. I a;so did a couple of small murals for our community. A retail store owner asked me to paint the ceiling in his dining room that was being renovated. I worked looking up every day for six weeks. By the end of the first week, I was looking for Sacramento chiropractors to help keep me working. I was not used to working with my arms raised over my head like that for hours at a time. The human body is not designed to paint ceilings. If the ladder or scaffolding is too high, you have to bend your neck. If it is low enough for you to look up and see, you have to paint with your arms over your head. I tried to paint while lying on my back as Michelangelo was reported to have done when painting the Sistine Chapel, but that approach only worked for me when doing fine detail.
The owner of the house brought me in a scissor lift so that I could easily adjust my distance from the ceiling. That helped a lot. It was much easier than constantly adjusting scaffolding too.