It can be done. 85 years ago, Germany emptied their country of millions of people without the aid of a single computer and using trains as the primary transportation. Truman deported millions of Hispanics in the 1950's using wired phones, buses and trains. It is not that hard. Easiest way to start is to START.
Step 1: Every single time you arrest a foreign scumbag for a felony, slate him for deportation as soon as his criminal proceedings are complete and prison term served.
Step 2: Every time you arrest a foreign scumbag driving drunk or stoned, hold them for INS and deport them immediately. 100% no excuses.
Step 3: Every time you arrest a foreign scumbag shoplifting, stealing, raping, molesting an underage child, driving or riding on a stolen car, jumping a turnstile or drinking in public, hold them for INS and deport them immediately.
Step 4: Every time you traffic stop foreign scumbags and they have no insurance or driver's license from any country, arrest and deport them immediately.
Step 5: If you cross the border at any point other than a legal border crossing, you get imprisoned until such time as you can be sent back. No matter what 3rd world shithole you came from. If you come from Iraq or Afghanistan or Chechenia, you get a used and decertified US Army parachute and tossed out of a cargo plane as we fly over your country. We give you a complementary set of jump wings before hucking your ass out of the plane. If you fucking come back, same process no parachute.
Step 6: Film every rally, protest and riot in this country. Use facial recognition software to ID foreign scumbags protesting our country. Arrest them as they leave the rally, bus them to nearest airport and deport them that night to wherever the hell they came from.
Step 7: Watch the rest of them carefully. As time allows investigate them. If their kids are in school getting good grades, mom and/or dad have jobs and have the yard mowed and pay their bills/taxes and none of them are fucking scumbags in gangs or committing crimes, evaluate them for permission to remain in America.
This is a good first step, shitballs first.