The best one is mine (not really mine, it's an old idea)
Scrounge a cartridge case- like a 223 off the range, or one with a split neck you're gonna throw out. Stick the neck and shoulder in a vice and crush it flat. Then file the sides of the crushed flat neck until it fits the primer pocket size you're trying to clean.
All it takes ius one twirl in the primer pocket, and it's clean.
Works as well as any brush I've ever seen, it's free, and it takes about 5 minutes to make- and I'm still using the ones I made 30+ years ago.....