I use my trusty compass and make a circle on aluminium foil. I carefully cut the circle out of the center, take the foil pull it tight and tape it to the model spray on the meat ball. Carefully remove the foil, wait for it to dry off and move to the next target. Sometimes I cann get four from one piece of foil. If it is big sometimes make a rough smaller circle and paint it the day before and use the foil to paint the edges. Fewer runs under the foil that way.