Water based mixing medium is NOT going to make a good glitter liner. It will make a good liner out of an eye safe pigment or shadow, but it doesn't have enough adhesive property to hold glitter as a liner without it getting into the eye (think of dipping your brush in water and glitter, thats essentially what you'd be doing). If you want to make your own glitter liner, i suggest picking up the MAC Pro Eyeliner Mixing Medium, it's a gel so it coats the glitter flecks and holds them in place so that no shards end up in the eye. Otherwise try Benefit SheLaq or premade glitter liners: Too Faced and Urban Decay both have EXCELLENT ones!