Painting outdoors in October in the Pacific NW is not a good idea so we decided I would paint on plywood panels
which would be subsequently installed on the site.
The site itself is oddly shaped so before I could start, the RTC management commissioned the creation of plywood panels sized to the site. [Technical note: The plywood used here is half-inch MDO (Medium Density Outdoor) plywood, which is specifically designed for outdoor usage, and is most commonly used for highway signs. It is generally weather resistant].
Removing the panels and moving them indoors was easier said than done, as plywood has significant weight. [Technical note: Three-Forth inch MDO is stiffer than half-inch MDO, but also weighs 50% more, which is not a trivial matter if working on pieces like this alone. For most painting or murals, half-inch MDO should be good enough, unless you specifically need the additional thickness and strength]
For the panels, I first sketched out a grid by drawing horizontal and vertical lines spaced 1 foot apart. (For lack of a 8-foot long ruler, I ended up using a piece of metal frame that I found lying around):