DIY question: spray-paint steel balls evenly
If I was going to try to paint a bunch of small steel balls with rattle can spray paint there are a number of steps that I would take.

Number One most important is to remember with spray can paint is to work at the correct temperature environment and leave plenty of time for full drying between coats.
Almost as important as the above item is to apply multiple thin coats instead of heavy almost dripping coats. This will become even more important with following considerations.
Acquire some square grid welded mesh wire material. For 3/8&quot; balls and 1/4&quot; balls mesh such as McMaster-Carr 9230T403 may do the trick. Following scale drawing shows the side view of mesh and steel balls:



Place the mesh in a sturdy horizontal position.
Hand place your balls on the mesh grid leaving space between them.
Spray paint the up facing surface of the balls with a light dusting type coat of paint and let fully dry.
Rotate all of the balls on the grid so that the recently painted surface faces down toward the grid and then apply another light coat of paint to the new up facing sides.
As long as you keep the coats of paint very thin a small overlap from layer to layer as you rotate the balls should be invisible.
Repeat steps 5 through 9 till all the balls have the desired paint covering. Rotate each ball before placing it down again. It may take five or six repeats to get them nice evenly coated with paint on each ball.