I purchased the flex polisher and a bunch of menzerna products hoping to do this kind of work.
Although ive had some good results, alas its not as easy as it looks!! Im pretty mechanically inclined, but I just dont seem to have the patience or judgement with this type of work and I dont get the results I would like. This takes hours of prep and hours of handwork.
The last time I did my roof, I reached too much with the flex one armed and i sprained my elbow, pinched a nerve somewhere and it hurt for a month. Couldnt lift a glass of water without feeling pain.
So nowadays I prefer to have pro's like you do it, and its worth every penny. You do good work.