Get the subject to tighten their mouth (smiling) to make it full. Draw thin dashes with the pencil and smear them inwards using a brush. Keep the mouth stretched while you apply the lipstick.
Take the Lipstick (Pure) onto a spatula (even if you are working from a stick) and apply it with a lip brush. First colour the middle of the lips and then colour the edges, working from the outside inwards.