This is one method, from MUD's textbook and it's pretty nifty:
"Eyeliner should be applied to the eye open, not closed. With the eye closed, ths skin may be pulled too tightly. When the eye is open, the eyeliner will not be smooth or even, so do not pull the eyelid as this will distort the shape of the eye, making application uneven. If it is necessary to pull the lid taut, do so by lifting the brow.
Have model look down during application. When applying eyeliner to inside corner of eye near the tear duct, the model should look in the opposite direction, towards the outer corner. When applying liner to the outer corner, the model should look in towards the tear duct. This will keep the lid accesible and taut."
I've done it a few times and it's works. It need practise though. I'll try and pull a video where this method has been demonstrated.