I love glitter. Earlier I said I was like a 5-year-old regarding fairies; well, I'm totally that way about glitter, too. I really like the way it looks under glass and have taken to covering the inside of mason jars with it, and then painting designs on them with acrylic markers like the ones above.
When I first started glittering jars, I tried mixing glitter and Mod Podge and either brushing it on the inside of a jar or swirling it around to coat it. The glitter always ended up looking streaky, though, and I got frustrated. Then I read some internet posts by other crafters that said some people use Pledge Floor Finish for this purpose.
Pledge changed my whole glittery life! All you do is swirl some around the inside of the jar, being sure to coat it thoroughly, and then pour it right back into the Pledge bottle. (It lasts forever this way.) Then put in a generous amount of glitter and shake shake shake those sparkles all around. Dump out the excess and pour that back into your glitter container - no waste there, either. It dries much more evenly and looks great.