After the paint was dry, I glued the split balls to the bases.
After the glue was dry, I was able to paint the rounded top portions of the mushrooms. I did it in this order so that I could hold onto the bases while painting the tops (and avoid getting too much paint on my fingers). After the red and green paint had dried, I used my little finger to add the white dots on the caps. The last step before they were ready for the bin was to add their little oblong eyes with a permanent marker.
The final result are these fun little guys. They fit perfectly into our Super Mario sensory bin! Although I think I see us using them for some other activities in the future.