Depends on their ability. I'm 51 years old, in good health. I haven't fired a gun since the .22 sleeved SMLE we used in Army Cadets in the 1980s. But assuming weapons can be had, the only help I'd need were Russians invading my town is a quick lesson on the workings of the Kalashnikov along with ammunition, and maybe a sandwich.
Until the rounds start flying, and mortars whistling in, and you shit yourself…