Blowing is correct. Sopletiar not. It means using the torch. This device consists of two ducts that join in a nozzle, a va acetylene and oxygen, that mingle and make ignition are driven out a flare of very high temperature and pressure. Generally used or to make welds or make cuts in metals pretty hard. In Colombia you also have other uses for the term blowing: one to indicate that we blow with force a duct or clogged hose, and intends that the air you uncover. It is valid for diving equipment or hoses from the vehicle. We also say blowing or blowing when a furtive way student helps fellow to respond a school exam.