The invention provides a method of manufacturing a golf ball composed at least in part of a spherical elastomeric body. The method includes the steps of extruding a bar of an unvulcanized rubber compound for obtaining the elastomeric body, cutting the extruded bar into slugs of a given length, and coating the slug with a saturated or unsaturated carboxylic acid metal salt in powder form having a melting point at or below a vulcanizing temperature. This method prevents the slugs from clumping together and improves mold releasability.