Since we are on the subject of the "Witnesses for Jesus" I don't believe the 2 witnesses or the 144,000 are doing this witnessing.
There is an unidentified group of anointed Christians that will have to preach "these good news of the kingdom and then the END will come ". Since the End is a specific period of 3 1/2 years of the Great Tribulation, this witnessing will have to take place during a peaceful time.These are the first 3 1/2 years of the "Peace and Security" that will be time of peace on the planet under the supervision of the Antichrist when he makes the "covenant with the many" at the begining of the last "week" of 7 years period according to Daniel.
Daniel 9:27:" And he(=the Antichrist) shall make a strong covenant(=peace & security) with many(=Babylon the Great) for one week(=of 7 years), and for half of the week he shall put an end to sacrifice and offering"