I read somewhere online (here perhaps) that the primer compound is still installed by hand in the factories. Pretty much a case of squeegeeing a wet paste across a plate full of cups.
I've read of the Russians using the strike anywhere match heads to reprime .22 LR, because it was their only option for ammo out in the Communist sticks of backwoods mother Russia. The written article was in a gun magazine, maybe 20-25 years back. They installed the compound wet, IIRC.
Whoever wrote up that bit on refilling primers, either purposely or out of ignorance, did all those that read it, a disservice, by not specifying that the primer compound (match head paste) be handled wet, at least quite damp.
As far as SHTF, who really thinks there will be a supply of strike anywhere match heads available? Not really commonplace anymore. The few places I see with wooden matches at all, have safety matches (no sand or crushed glass to help the ignition) that require a finer friction surface to work. Even then, the tweakers have wrecked that source, as the match heads have been used as a source of phosphorous for use making meth, IIRC.
It's gettin' so that a kid can hardly get enough education and supplies together to make a damned stink bomb these days!
The Tap-O-Cap. Read enough reports of accidental discharges from seating the cap on the nipple to wish to stay well clear.
The FreeChex tool supposedly works. I won't swing a hammer that many times to make a gas check. It starts with using a hole punch to cut out circles of pop can material, then uses a different punch and die to shape them. Sort of. The pictures I've seen looked pretty nasty. YMMV.
The Corbins want to be paid rather too much for their time to consider, IMO. Nice workmanship, but lots of coin.
Over on Castboolits, there are a couple different options. A poster by the moniker of patmarlin has a design he is marketing. His uses strips of sheet copper, also available from him. About $100 Cdn, plus waiting time while he spools up some production.
There are a couple other designs that are not being marketed, but are a little more elegant, that can be seen there (look for a thread titled "A new source of gas check material for those that roll their own" on the Castboolits sub forum, among others.
I'm about half done making a gas check making set. I have a punch that works to my satisfaction for cutting discs, but have not got a decent working model of the forming tool yet.
Cheers
Trev