Like many have said - Builders bog is the way I go.. just don't mix too much at once as you only have a certain amount of time to work before it goes off.
To fill playfield divots I either use Plastibond ( like builders bog but a bit plasticy) or Tamiya filler from hobby shops.. the Tamiya comes out of a tube and can be applied using a clay model spatula.
Bog on a cabinet will sand back dead smooth but the timber wont.. youll get " grain raise" when you prime it and this needs to be rubbed back to smooth.. its a quick job as you are only taking back where the grain has absorbed the primer and swollen slightly... rub this back and reprime and you should get a real smooth surface.. or you can skim fill as Marty suggests