Hello Penny,
I just picked up the messages today .. Thank you very much for your explanations on the grey undercoating. I just realized also that the JoSonja paintings are acrylic paints, when I read your water dilutions.
So you coat the metal surface directy with this very diluted painting ! I recently tried to undercoat a flat 30mm with acrylic dilutd paints, but it took many layers to built colour, as pigments are very dispersed in dilutions 1:4 to 1:6 and anyway, and I ended up (impatent) with an excess of pigments built up onto these little surfaces.
Your final coats seems to be opaque enough to have meta totally unvisible. Do you get the highlights with more coats ( as we would built painting of a transparent cloth on a skin) or a brighter colour ?
I will look more to your previous explanations on this pre-coating on articles on another forum, and try to use on a larger flat than 30mm, perhaps with different colours close to the final oil paint tones.
I congratulate you for the very special lightning atmosphere created on your final painting, similar to the the "clair-obscur" (Chiaroscuro) of Caravage, the Dutch school after, and Georges de la Tour !! Magnificient ....