M2 Shutter Release Collar Stuck

[Shutterspark]

Does anyone have any tips for the removal of an extremely stubborn collar, short of sending it to a repair tech?

So far I've managed to mangle several brass and aluminium flexi-clamps trying to get it off but it won't even budge, it's as if it was welded to the thread.
I've also tried rubber stoppers, rubber sheets and a rubber tipped dowel.

I'm considering buying a set of stainless steel flexi-clamps so I can apply more pressure before the metal gives in. Good idea?

Trying to avoid sending it off because all I want to do is replace the felt washer for the exposure counter. This is the only body that's ever given me so much trouble.

Any help would much appreciated, thanks!

[Landshark]

I've used a TINY drop of penetrating oil for threads that I couldn't loosen. Apply it and let it sit overnight to work.
I do use a pinpoint oiler or hypodermic syringe to control the amount of fluid.