If it was done properly with the right resources, buses, plenty of agents, aviation to fly them back to their home country many of them would leave on their own just as during the Eisenhower administration. Suspend their rights to a hearing before an Immigration Judge, no appeals, no asylum, if they’re unlawfully present they’re subject to immediate removal. Advertise heavily on tv, radio, social media. Let them know that immigration agents are coming after them and a lot of them would pack up and leave.
Make the corrupt employers who have been hiring them pay to send them back.
I used to enjoy seeing the requirement for all aliens to register every January as to where they were located.