Moisturize first, always. Then imagine drawing a halo on your face that goes from forehead to chin. Take your perimeter shade and apply it starting from your hairline to about a half-inch out. In this case, Martin is using a liquid foundation shade (Dior Backstage), which he blends in with a brush.
Next, apply a light layer of your secondary shade everywhere else with a brush. Use a sponge to gently buff in and blend where the two shades meet so that there isn’t a line of demarcation.