In reality, my crew, with its 25 year plus experience using acrylics on metal roofs, encounter few problem resolving leaks. Both the crew and I are oriented toward resolving leak problems first, then addressing rust and appearances. In my 20 plus years of working on metal roof restoration, my observation is that after leaks are resolved, then the roof's appearance emerges as the most important issue. For that reason, there are numerous pages here on tints and other techniques to improve a vintage roof's facade.
With scarfs, jackets and boots, the crew can perform the work in below freezing temperatures: