No one has ever mentioned that, LOL.
No one mentions picking up taboo skills like explosives and counter intelligence either:
Learn to do your own demo. I won't tell your our plan, but in Lucifer's Hammer the local yokel's blow up a bridge to keep the city folk from reaching them.
Good advice. You can also do like the French Resistance and change signs and set up "fake but accurate" detours around your perimeter. This of course assumes GPS down/internet switch flipped, etc.
99% of people fleeing something would take this detour. If this counter-intel sign (a ruse) is compromised by someone, thats where you can get your QRF to intercept well before they reach your compound.
A sign like this may very well be on the way to our retreat, with a couple of "good ole boys" with trucks blocking the route.
As far as explosives, stay legal...nothing will land you in the fed pen faster than explosives and machineguns.....nothing.
Oh, did I mention that you should be skilled in use of chainsaws also? Learn how to weld/build an Abatis, blow/dig culverts, stretches corduroyed with felled trees, etc:
Good luck...Disclaimer: I really hope this stuff never gets used outside the educational realm.....and in complete accordance with applicable federal, state, and local laws. Also, every post by me is for morbid senses of humor for education purposes only. Do not attempt! ;)