Usually the foreign employer takes care of those things. A Vet should not need much more than their DD214 (Honorable) and a passport. I’m sure you can acquire both. The passport takes about two weeks. DD214s can be obtained online.
Why Vets? Just consider the working conditions and lack of supervision. A labor pool which will get to work on time, refrain from drugs, have team focus and discipline and aversion to crime is invaluable in the back country.
Why Vets?
In short...good work ethics.