Where to start to learn how to do minor repairs

I have a collection of phonographs from the 1920's. I was told the original finish was usually a pyroxilne Laquer. Some of these pieces have fading, scratches, and other wear.

I would like to learn how to make simple repairs myself... What is the best way to get started? I bought a can of the Behlen Jet Spray laquer but am not sure the best way to use it so it sits on the shelf. These are fairly valuable pieces and I don't want to make them worse!