Metallic spray paint looked too perfect, not antique and weathered enough. So I hauled out my paint-box and went to my favorite colors used in other projects. I wasn't sure how acrylic paints would work with this 3D-printed model, but they adhered well and gave me the texture and imperfect finish I was after. (see it unpainted straight off the 3d-printer here)
Sometimes the oldest and simplest techniques are the best. I brushed on the paint them wiped off portions of it to reveal the black wrought iron, er... the black PLA plastic underneath. I did not smooth it down again, so clumps formed along the edge like something that had been painted and repainted for decades.
I plan to add some more weathering - if I can remember how to do that. The technique is simple, but getting it to look right at this scale can be tricky. This is the first coat of paint, and as I remember I need to add some darker patches, some light and dark greens in the corners, then some bright patches in the "worn" areas.
And I really want to try the two-part instant patina paint systems. Apparently, the two paints interact chemically and give a very realistic antique verdigris without all the multi-layer painting. I'm all for adapting new technology, especially if it saves me time.