I use a drop or two of the mixing medium on the back of my hand, then dip my brush into it to make it damp, then I dip my dampened brush into my pigments and apply (this intensifies the color and makes it stick better).
I believe a lot of the glitters are not eye safe (as mentioned already) - A friend of mine got a terrible irritation and swollen eye once because the glitter got into her eyes. But I do it anyways...guess I'll learn my lesson one of these day lol. But you can apply your mascara and before it dries, dab on the glitter or use the lash mixing medium that MAC has.