Dirt seen thru the view finder on an F5

[Robert Nicholson]

In general what can people do to maintain viewing clarify on an F5.

I'm told it's unwise to clean the mirror or the screen but the Nikon
rapair place in my area said just the opposite. I'm willing to bet 
that the mirror on the F5 can take a lot of punishment. 

Is compressed air appropriate for an F5?

Sending cameras to Nikon is out of the question.