I would go one better and do it precinct by precinct. The counties are unusually large, especially Los Angeles, San Bernardino and Riverside, which are bigger than some entire states in area (and population), and many areas within them don’t subscribe uniformally to the moonbat derangement.
Precincts must vote 55% for secession (anything below 55% can be swung in the “right” direction). The Commie RED areas can have their dystopian fantasy world and the Conservative areas can remain with America in a newly constituted Golden State.
I would send the YES voters to camps for re-education and labor, and keep their property and land.
Another way is to give each person three choices of where they want to live. Each state would determine the net number of people (Ins - Outs) they would accept. Computer simulations could easily determine population shifts and their effects (jobs, house prices, Congressional delegations, etc.) Then people can move to their new states with one coming back. Everybody gets the political landscape they want.
Naive, yes. Practical, probably not. But it’s novel.