Been trying to figure out the best way to prime all these little magnetized pieces that come with the new Mk4 warjacks. They can get blown around by the primer spray if you just lay them on a flat surface, especially the heads, and paint can pool under them as well.
I finally decided on the old tomato can method. Makes it easy to get them from all angles, all in one lot.
I stick mine onto magnetic rods and spray them individually for an even coverage but then stick them onto an old trophy bowl made of brass, in a very similar fashion as you do. Then I can keep them held there while I paint them, so it’s also easy to pick one for painting and them put it back to dry. The magnetic rod doubles as a handle during painting.