Hi, it is a lovely highlighter, however I would experiment with it and see what would work best for you. For example, when applying ontop of foundation, use your fingers to dab on the foundation - as I find that it wipes off your foundation if applied too heavily or with the brush it comes with.
I love putting it all over my face after primer for. Luminous natural glow, once your foundation is applied on top, your skin will look healthy and glowy.
As for longitude, for me it lasts all day once applied.
Another tip would be to mix with your foundation, but overall a good product if you want to try it out.