i think a brush or sponge is best for you, as it assures you have a flawless finish,
as long as the colour is a perfect match to your skin (its always better to go a touch lighter than darker if stuck between 2 shades... as you can add blush/bronzer to add colour) you dont need to apply it all over, you can apply it where its needed, for example the nose or forehead.
not to say DONT apply it allover, I apply it all over myself, but some people prefer to just cover the tzone area.
A nice option is mixing your foundation with a highlighter so you get a 'fresh glowy' look.
just experiment. hope that helps