We decided to use wood to trim around the exterior of the windows, even though S had painstakingly removed every piece of aluminum siding trim with hopes of reusing it. But because we made the window openings slightly larger than they were previously, the aluminum would have been a giant pain in the neck. So after S re-attached the aluminum siding edging, cut off the over-expanded Great Stuff, and stuck on yet another strip of waterproofing tape around the edge of every windows, it was off to the 'Depot again for more supplies.
When S returned from the 'Depot I sent him outside with a can of primer and an old paintbrush so he could hit the ends of each cut of pre-primed wood with a little primer before nailing it up. S measured the first length across the top of the window, cut piece of trim board on the miter saw his dad dropped off earlier in the week and cracked open the can of primer.
So back down S came, trim was tossed on the bushes to dry, and the hammer was placed back down on the ground as S grabbed his tape measure, a pen, and a tiny piece of paper. Back up on the ladder, S measured the width of the trim space every five inches and wrote the measurements on the tiny piece of paper.