Once the hardener is mixed into the primer, it very difficult to clean brushes.
The purlins can be initially first pop-riveted to the rafters, then when the all adjustments have been made, welded to them. The photo really shows all the elements of the roof structure; the 40cm center girt at the ridge, the 35cm rafters, the collar beams and the purlins. The purlins support the long span steel roofing, but before the roof itself is put on, a metal “facia frame” is installed around the perimeter of the roof.
The other parts of this standardized system are a steel frame welded to the ends of the rafter tails.
This “facia frame” extends around the entire roof edge.
You’ll also have to buy epoxy reducer, an expensive thinner for epoxy. Some of my crew members tended to waste the reducer, especially trying to clean brushes.
Finally, I learned to buy cheap brushes which could be discarded.