Finally found a couple spare hours where i attempted to recreate my happy accident. This time I deliberately did not add the patina until the Swellegant metallic coating was dry. This time I used copper metallic coating instead of brass. After baking, I added the Pearl EX varnish and once again the patina blossom occurred. Instead of a green tint one would expect with verdigris, I got more of a blue tinge to the patina. It is still a pretty color.
After adding varnish
The sparkly bits are from some copper foil I added.