Focusing Screen Fungus

I have a Nikon FE with a focusing screen that has a spot of fungus right on the focusing aid.

Is it possible to take soapy water and apply a scrubbing force with a Q-Tip on the aid or will this ruin the screen?

I believe that the screen comes out and is replaceable. I sure would tread lightly. A tiny bit of alcohol + water (vodka like) would be my first choice, realizing that you might ruin the screen. Another thing I would try first would be a dry camels hair brush.

I believe I'd use a small artists' brush and a drop of Joy and warm water, then rinse and dip in distilled water. If you go "scrubbing" with anything it will be ruined. BTDT. Don't do anything to it you wouldn't do on a lens. And a lens is glass. This is just plastic. If you have to do a "scrubbing force", it's already etched and no good. Chances are it hasn't come to that though.

The FE focusing screen is removable - IIRC the FM's is not. It is just a single piece of plastic, which is good (for multipart screens you have to be careful about getting anything in between the layers).

I have never ruined a focusing screen with alcohol, but recently I found a plastic focusing screen that I suspect was ruined with alcohol or a similar fluid. While researching another topic (cleaning plastic and rubber woodwind mouthpieces; it also appears to be an issue for people cleaning car headlights), I discovered that if alcohol is strong enough, it is known to attack certain plastics including acrylic. So I would now be real careful about using alcohol on a focusing screen. It apparently depends on the concentration: weak solutions like lens cleaning fluid or 40-50% (vodka) might be ok, but 75-90% (drugstore rubbing alcohol) might be a problem.