You can't. The US is essentially Mexico's wellfare system. We're not getting their doctors and lawyers, we're getting their unskilled laborers and people who can't cut it in Mexico. The one constant in every society is that the unskilled and uneducated always feel entitled to the property of others. They will vote Democrat because Democrats promise them free handouts paid for by us. Nothing can change this because you can't change human nature.
We do get some of their very good ones who are disgusted by the system over there. Many of their doctors and lawyers are useless because they were just rich kids who could buy their way up. The way the system works is the 10% elite class makes sure their own kids get the high paying jobs even if they are stupid. The one who told me that was a guy in Mexico studying to be a lawyer and we were asking if they have the bar exam like we do in the US. He said yes, they have to pass a bar exam and then they can practice law and if they don't pass it they can pay a bribe and then practice law.
And by being the property of the Democrats they have little incentive to ever become productive. The Democrats will just keep building on the permanent underclass, which underpins their political base. Why the GOP can't see this I'll never know.