Applying eye liner on water line

I'm 39 and remember that, as a teenager, I used to apply my eyeliner in the surface of the lower lid. I haven't done that in years, and now I've started to wear contacts. I know it's a pretty standard method of applying eyeliner, but it kind of makes me nervous because it doesn't seem sanitary, and I wonder if it will flake onto my lenses and cause eye irritation or worse. I know some people even apply it on the UPPER lid's water line, which I've never even tried.

Can you please advise on the right and/or wrong way to apply inside the lash lines, which is the best liner to use for this, and how to keep from getting bacterial infections (i.e. do you replace the liner often? Would constantly sharpening it help?).

Thanks!