It is eight feet by sixteen feet on four sheets of marine grade plywood. This should stand up to Chicago winters pretty well. First, we primed the plywood with a couple of coats of Killz Primer.
We used a projector to trace the image (in my darkened garage) and then filled it in paint-by-numbers style.
We painted with six shades of exterior grade house paint. Our painting "map"
It got pretty confusing at times.
Finally, we sealed the mural with four coats of water based spar varnish and then an anti-graffiti sacrificial coat. My pa helped us mount the four sheets of plywood to a brick wall with Tapcon concrete screws and a hammer drill.