I am going to set up a money exchange in Barbadoes. Mexicans in the US wire the money to the exchange there, who then wire it to Mexico.
Apparently, high finance ideas like that are over Trump's head.
I don't think they're over Trump's head, he's probably got a lot of cash offshore. However, I do think that Trump knows his plan will never work, but it sounds simple and plausible to those who follow him.
He's like any good salesman, play to what the customer wants, and tell them you can provide it (even if you can't). Then, when the customer comes in for the product you promised, you do a bait and switch and tell them that it just sold out.
Trump is promising a lot, but if he actually ever got in, he would immediately do a bait and switch.