Try dabbing them on at the just above the middle of your lips (just above the cupid's bow) to make your pout look fuller. Otherwise along the top of your cheekbone or on your brow-bone will help your face appear more angular and slim.
The pen packaging is also very convenient, you draw it on and then tap to blend with your ring finger, they are also very compact and will fit into most make-up cases, and you can even slide them into a brush roll without any fuss.
One thing that I think Touche Eclat has over Touche Magique though is the variety of shades, Magique comes in four shades (in Aus) while Eclat comes in seven with varieties for darker skin-tones.
Yves Saint Laurent Touche Eclat
L'Oreal True Match Touche Magique