Easy - deny them everything. No welfare, no schooling, no jobs, nothing. They’ll self deport. I can’t see what the problem is. Use Mexico’s illegal laws.
“As a start, we should make it completely unfeasible for illegals to stay. No school. ” California did try this years ago. It was called prop 187 and was voted overwhelmingly into law. Then one lousy federal district court threw it out and the governor refused to appeal his ruling, hijacking the will of the people once again.