liquid eyeliner should only be used on the top lash line.
Choose one that is close to your skin tone to use from lash line to brow bone, then apply a slightly darker one to the crease and blend up and away.
You can apply them heavily across the upper lash line and then smudge with a sponge or a pointed brush.
Gels can be used along the upper lash line for a polished, yet natural look.
Simply dip the very edge of the brush into the shadow and drag it across the lower lash line.