National Guard or regular army? Are you going to screen them to make sure Hispanics aren't in the troops? What about the Canadian border? What about depleted manpower overseas?
Special training? Could Border Patrol do this? Shoot to kill, arrest and repatriate, or stand around and look fierce? Armed with what weapons?
Lots of things to think about with your suggestion.
Also, what about the coastlines?
Diff between you and I, is you dredge up defeatist reasons why it can not be done. When reality it can be done. Same as we've done in Korea and other situations. Getting troops on our Southern border to deter illegals is as easy as pie and scares the aficionados of illegal immigration.
We just set up a base in Qatar in record time. Do the same on the Mexico border but make that 3 or 4 smaller bases.