More useful: Volunteers to augment understaffed Sheriff's departments and police forces in border-area towns and counties, providing 24/7 guards for grocery stores, gas stations, schools and churches, as needed, where needed. Working under the legal authority of a local sheriff's deputy empowered to make actual arrests, a mix of about 6-8 such volunteers in a pair of pickup trucks to each deputy would seem about right: enough to perform guard, observation and LP/OP duties and assist with prisoner transfer if so ordered. Some isolated ranches and trailer camps may have similar requirements. By the way: it's a Felony crime in Texas for anyone other than the owner to cut a stock fence in Texas.
And it should keep the rock and pop-bottle-with-gasoline throwing to a minimum, just in case any of the sneakier ones- or the ones already here waiting with supplies- make it past CBP and the military forces at the border.
Great ideas!