OK...here is how you do it...
Make sure that nobody wants to move today. (if they do, and its not someone you want out, tell them NO)
TT 4 days BACK. Save.
TT 4 days AHEAD. (same day you started with).
Walk in front of every villager and someone will ping you to move.
Just be sure to say NO to everyone you want to stay.
This has worked without fail for me for 30+ villagers.
Most important is to be sure that when you walk in front of a villager, they actually "see" you (not fishing, talking to another villager, etc)
- - - Post Merge - - -
Talking to Isabelle and ignoring DOES NOT WORK...it was purely coincidence if you think it did... Moving out is completely random in every way possible.
IF a villager says "naw...I changed my mind" after you agree to have them move, CLOSE THE GAME without saving. They will ping you again, the answer changes each time. BUT then, do NOT speak to them AT ALL until they are in boxes...no matter how many times they ping you!