Well, it WAS years back. Maybe I sanded them and don’t recall it. Just seems like I’d have used some sort of tool for the 1/2” stuff, instead of fat fingers, and I don’t have anything like that in my ol’ plumbing tool box...
Some of those fluxes 40 years back were really aggressive, too...
Usually it’s a cheap wire brush, male on one end and female on the other - they get worn out, clogged up, rusty and useless pretty fast, so since they are cheap I often throw them away when I’m done a plumbing project - maybe that’s what happened.