Tom
That's a crazy rare gun. I want it!
That's not the one we corresponded about is it?

First do no harm
So, start with a simple washing with detergent and water

Move up to an oil based non polar cleaner maybe paint thinner

If that doesn't remove crud, go the other way to window cleaner
Then maybe an ammonia based cleaner

I'm feeling generous today
I can send you an ultrasonic cleaner for the action.

There's many liquids that work great in them for guns.

Out there doing it best I can.