Aside from USMC training, I have also taken two CCW classes.
The first was some old former LEO who spent nearly the whole time talking about how cool he was.
Put a check in the box, passed the class, got permit.
The second was by a former Army ranger who also did 5 years as VIP protection in the Green Zone in Iraq. He and his assistant were good. They put me through a series of drills outside the regular permit training.
As for carry post-SHTF, eh, I figure if the ROL is out the window, everyone will be carrying, be it handgun or rifle or both.
Not that I am expecting MZBs at the gate, but I likely would.
A few years ago two fellons escaped a supermax prison north of where I live. Various reports had them anywhere from in the area, to NYC, to the Caribbean. No one knew where they were. More than a few carried around here, permit or no.