[The Philpott]

Easy with the contact cleaner so you don't get it in other moving parts!
The cardboard tube inside loo roll is abrasive enough (and the right thickness) for cutting strips off and cleaning those contacts. I use it soaked in contact cleaner (dry then wet then dry)
Best of luck with the ohms ranges, most problems are solvable, often down to elderly potentiometers making zeroing difficult. A low mileage meter will be less problematic in this respect.

Dave