Update: I stopped dunking stuck focus rings in lighter fluid 3 weeks ago, and I was an idiot for doing it for so long
Had a customer's 50mm f/1.4 come in with a focus ring that wouldn't budge, so instead of the usual fluid bath I just warmed the barrel with a hairdryer for 90 seconds and it spun free. Turns out the old grease had hardened, not glued itself in place, and I probably wrecked a dozen helicoids over the years for nothing. Anyone else here got a lazy fix they kept doing way past when it stopped making sense?