Although for some unknown reason they're marketed as a "mastering" tool, it's a pretty rare occasion that you'll find a mastering engineer actually using one.
Many of us refer to them as "maul-the-band" compressors.
The only tip you can ever use for anything - mixing, mastering or otherwise, is to do what your ears are telling you to do.
(If they're telling you to use maul-the-band compression, I'd be far more concerned with why you'd need it than actually bothering to use one)
What if you're only mastering one band's music at a time. Don't you only need a multi-band compressor if you're mastering more than one band at a time????
What if you're only mastering one band's music at a time. Don't you only need a multi-band compressor if you're mastering more than one band at a time????
Just because it's multi-band it doesn't mean that you have to use all of them. Use an MBC to control a frequency balance issue that is dependent on dynamics. A de-esser is an example (a single band of MBC can be used for this) as well as a loose bottom end.
Don't just throw the thing over the entire mix though and expect magic to happen, use it to attack a specific problem like any other tool.