Methods for post-mold processing a Venturi device for generating vacuum are disclosed that improve the evacuation time thereof. The methods include providing a molded Venturi device having a body defining a Venturi gap between an outlet end of a converging motive passageway and an inlet end of a diverging discharge passageway, where the outlet end defines a motive exit having flash extending radially inward and the inlet end defines a discharge inlet having flash extending radially inward. Then, the method includes positioning the molded Venturi device with an inlet end of the converging motive passageway facing a blasting nozzle or with an outlet end of a diverging discharge passageway facing a blasting nozzle, and propelling blasting media into the motive inlet or the discharge exit of the Venturi device to remove the flash in the motive exit and in the discharge inlet, or vice versa.