I have gotten an old hand held DMM that had gotten some paint spilled on the LCD a long time ago.
Speaking of old

I have tried measuring resistance and voltage with it before but never gotten any good readings with it; the ohms was swinging between 0 and 50 when the test leads where shorted.

Today I figured I should try to clean it off as it is hard to read the LCD with paint over most of it.
I used some nail polish remover to get rid of the paint and when that was done I was able to see the decimal dot on the LCD.
Once I could see this I knew it was time to change the battery [On this DMM the decimal dot flashes when it is time to swap battery].
I am a bit surprised that the DMM even came to life, it should have a 9V battery. The old one had a best before date of 2001 and held all of 4.2 volts.

With a fresh and stronger battery the readings got a lot better, for instance with the test leads shorted now it reads about 0.2 ohms.