Just one, let a pro do it!
Getting thirty-seven feet of stripes to lay down and look straight was a major task. I had ordered more than required so was able to try about six feet. When I realized how hard that was, especially without a real and long scaffold, I turned it over to a professional.
Well, now that I see the picture I guess it was more than six feet. The waviness doesn't look too bad here. This was all removed by the pro. Then I cut the bottom two stripes off of the roll and went with three instead of five. The bottom two were just too thin.