Hi
You could use glass and tile medium, then let dry 24 hours and paint with your regular craft paints. I think the glass and tile med. gives a frosted look. Don't remember to well. So paint only on the area you will put your design on:)

hope this helps,
Karen:)
OSCI

Other than regular acrylic you can also use one of the acrylic enamels available such as Delta PermEnamels, Plaid's Apple Barrel Gloss Enamels or DecoArt's Ultra Gloss Acrylic Enamels. They're great on glass. I prefer the latter 2 because there is no prep or finish required. The Delta brand has 3 steps.

I am also thinking in painting some designs, may be flowers on a large bathroom 9 years old mirror, that somehow at the bottom has grey large spots that is not a mirror anymore in these spots, the solution would be to replace the mirror but it would be costy....so I was thinking to paint some decorative designs on it, what do you think? Has anybody done that? what paint should I use? any other recommendations?
THANK YOU