First time setting sag

Use some penetrating oil, let it sit for awhile, then use a flat blade screwdriver and tap it loose with a hammer.

CRC freeze off works miracles!

A can of penetrating fluid (I use Panther Penetrant) and a brass punch will be your best friend in not damaging the lock ring. Make sure you're using a big hammer and hope the threads are still there when you're done. Best of luck!

Deep creep soak and then a punch and hammer. If it doesnt work, pull the shock off and use a spanner wrench and a cheater bar to get it loose.

Simple tip but sometimes forgotten. It's easier to spin when the rear wheel is elevated.

Here's a "no duh" suggestion: make sure you are going looser on the lock ring first. Once the lock ring is threaded away from the adjustment ring, you can grip the shock spring and rotate the adjustment ring with it (no punch or screwdriver needed.)

one way of figuring out if your spring is right for you, is set the bike to a static sag to 30mm from stand to its own weight, then gear up and sit on it, depending on what measurement you get from it, ideal setting and weight for the bike 30mm of static sag, should equate to 100mm of race sag, if your less than 100mm your springs too stiff, if it's more that 100, your springs too soft.... but that's once you get the lock rings loose.