Backing up just a bit, here is what my husband, son and I accomplished on Sunday, when the builder wasn't here:
I am huge, huge, HUGELY grateful that they cleaned up that terrible pile of cedar siding that the house contractor left behind! And they were able to salvage me quite a lot of good pieces.
Meanwhile I worked on re-treating my steel roof panels. When I first did it, I diluted the vinegar half and half with water. And leaned them up against the fence so the solution could run down the grooves. My idea was to start some rust stripes. But I realized that the vinegar just beaded right off the metal. It had no effect. When I looked up how to do a better job of it, I learned that even straight vinegar is pretty weak, so diluting it was just a big waste of time and vinegar. I guess people put salt in the vinegar to make it work better. And someone suggested making a salt and vinegar paste and scrubbing it in, to rough up the coating on the metal.
So for my second treatment I laid the boards down flat, sprinkled vinegar and then salt all over them (1 at a time), and brushed the resulting sludge lengthwise with a push broom. Then I left them laying flat to maximize how long the vinegar and salt could be in contact with the metal.
I let that sit overnight, and then I poured small amounts of straight vinegar in each channel, and tilted each piece until the vinegar reached the other end. Then left them laying flat over night again.
After two days of the revised treatment, this is how the metal looks now.
It's beginning to have the striped effect I wanted. And hopefully that will reduce the glare, once they are installed on the shed.
I'll have to ask the man if he cares whether I rinse the salt off or not. I'd like to let it stay on as long as possible, until the rain washes it off.
Not sure if it really matters to you much but if the salt runs off the roof panels and onto the ground when it rains then the grass around the base of your shed will be killed and depending on the concentration of the salt you may not be seeing grass there for many months to come.