With an idea that a commercial corner roller could be implemented in painting these standing seams without having to bend down I finally use the one I bought years ago in anticipation of rolling in interior wall corners. After a couple days use it is falling apart. Presumably from the interation of the paint medium's Xylene with the closed-cell foam. Not wishing to go back to brushing the seams bending over or kneeling I made a new roller core shape out of plywood, then delicately perform the surgery of sewing it while still soaked with noxious Hammerite, as cleaning it would have been a long process. (At the end of the project it will just go into the trash.)
I resolve to try and take pictures of progress from a further distance, since it is a larger edifice, and more prominent for it's more decorative flourishes.